This lecture will help you to examine your lifestyle and needs realistically: Examine yourself functioning with the help of a service dog. 
The characteristics that come out of it should help you to narrow down the choice of breeds and individual dogs that you can then look at as a service dog candidate.  

Here is the link to the Needs Assessment in Excel spreadsheet format. =16pxThis will provide details about what characteristics your service dog will need to have.

It is interactive which means you can save it to your computer and type in your own details.
https://www.dropbox.com/s/xew4dj2s7nu7c5f/Needs%20Checklist.xlsx?dl=0

Here is a pdf version to download and print off. 
https://www.dropbox.com/s/drf160jada8kc4e/Needs%20Checklist.pdf?dl=0

Place an X any of the lines that apply and fill in the information as it applies to you. This checklist will help you to determine the characteristics you need in a service dog. Keep in mind, that you are looking for a dog that will be able to be used in public and be unobtrusive except when needed.

Below is an explanation of each line. The one thing about any breed and individual dog is to choose one that matches your lifestyle. If a dog doesn't fit into your life, it won't work overall.  

1. Tasks you require.
Go through the tasks lists provided by the IAADP and make a list of all tasks you need your dog to do for you now or in the future. 
http://www.iaadp.org/tasks.html

http://www.iaadp.org/psd_tasks.html 

2. What natural skills your dog will need?
There are breed tendencies that are genetic. Some examples are retrieving, bracing, blocking, scenting, herding. Your training job will be easier of you consider dogs that have a natural ability to do the tasks you need them to regularly do. 

3. What other plans to do have for the dog? 
Some people enjoy doing dogs sports such as agility or freestyle to keep the dog in shape and engaged. Others enjoy competition obedience while others like skijoring. 

4. Consider how your income may affect the dog you choose.
If you have a limited income, this may be an important point. The initial purchase price is small compared to ongoing costs like feeding, grooming etc. Larger dogs eat more, non-shedding dogs require regular clipping by a groomer. If costs are an issue, always keep them in mind or be creative in how you get around such costs. Is there insurance you can get? Can you do fundraising? 

5. Where you live may affect your choice of dog.
A large or very active dog in an apartment usually does not work well. A small dog among large horses on an acreage may not be a good idea either.  

6. Who is living with you? Do you live alone or with others?
If children are involved, breed selection becomes more important. Some dogs do not tolerate children, even if they are raised with them. The dog needs to be comfortable at home as this is his time to recover from work. 

7. Are there other animals in your home or yard?
If so what are they? Some breeds have a hard time adapting to living with other animals while adult dogs may not adjust to such animals if they were not socialized to them when they were young. 

8. Do you have another dog at home that is fearful?
Since dogs are social learners, and puppies learn from adult dogs, you are setting your service dog pup to fail if you raise it with that dog with the expectation the puppy will become bombproof. If any public training is done in the presence of the fearful dog, the pup observes it. Dogs emulate other dogs both in functional behavior and dysfunctional behavior. You may need to consider rehoming your current fearful dog to a family member or friend if you are serious about training your own service dog. If you adopt a solid tempered adult dog as your candidate, you might be able to manage the situation so the adult dog does not see your fearful dog react. Hopefully, his own temperament is set enough that he doesn't learn any unwanted fears or undesirable behaviors from the fearful dog.  

9. How much travel do you do?
If you do much, the breed must be comfortable with strangers and small spaces. 

10. Is it local travel via car, bus or subway or is it further afield via plane?
Size may be an important consideration for other people if you are crammed into small spaces with them for long periods. 

11. Allergies-Do you, a family member or helper, or those around you at work or school have dog allergies?
If so, this may affect the type of fur you choose. The non-shedding breeds tend to be less allergenic. (There is no such thing as non-allergic dog). 

12. How active are you?
Different breeds and individuals have different activity levels. You need a dog to match you. Are you low, medium or high energy? A low energy dog will not be able to keep up to the busy lifestyle of a high energy person or vice versa. Look for breeds that match your energy level. One thing to be aware of is that in many breeds, there is a difference between the hunting lines and the conformation lines.  Look at the specific lines they come from and what they have been bred to do and what titles they have. Hunting lines alone tend to need more exercise than those from conformation lines. They tend to be higher energy dogs with a thinner build and faster metabolism which means they eat more. Their coats are different as well. Field dogs tend to have coats that are practical in the field (shorter, longer or thicker as needed by the terrain to repel water and burrs). Conformation coats are designed to look good. A great example of this is the golden retriever. The field lines can be very high energy dogs who need much daily exercise, and then there are conformation Goldens like the dog off "Homeward Bound, The Incredible Journey" with Michael J Fox who are more laid back for both exercise and temperament. I've had two of the latter and they were wonderful family pets and made great therapy dogs as they loved people and were sensitive to their moods. A field line golden would have been too much dog for me to handle.  

13. Are you an extrovert who likes people or an introvert who likes time by herself?
Again, choosing a dog that is similar to you helps. Be careful not to choose a dog that is too aloof though as even if you are not good with people, your dog needs to be. 

14. Are you fearful or confident in public or somewhere in between? Both people need to be careful to choose a dog that is generally confident. A fearful person needs the support of a confident dog, but not one that is so confident you can’t control him. People with medium and high levels of confidence do better with dogs that match their confident levels in public.

15. Do any of the tasks you require dictate the size of the dog needed?
What is the size? small  medium  large  extra large 

16. Do you have access to in-person dog classes or access to many other well-socialized dogs?
If you do not, you may want to err on the side of getting a dog breed that tends to be more forgiving if he doesn’t get as much dog-to-dog socialization rather than one that required extensive socialization to be neutral with other dogs. 

17. Will your disabilities interfere with or limit your ability to socialize your dog with other dogs, people animals, locations air events and you cannot hire help to do it for you? Again, select a breed that tends to be more forgiving in areas of socialization, resilience and confidence. Golden Retrievers, Labradors, hounds and others are good choices for this. Guarding, fighting and protective breeds tend to need heavy socialization to be useful in public. 

18. If you are unable to do it yourself, can you hire someone to help you with early socialization and ongoing training?  

19. Does dog need to be able to take direction from more than one person?
For example, if your disabilities don’t allow you to do some of the training or you are feeling well enough to do the training over several days, will the dog be easily able to switch to training with another person? As well, once trained, the dog will need to accept other people helping you in public. For example, emergency personnel who come to take you to the hospital or members of the public helping you if you have a seizure? 

20.  How sound reactive does your dog need to be?
An ideal hearing alert dog is calm but ready and willing to jump up from a sound sleep to alert you to a fire alarm ringing. A dog that is less reactive to sounds would be harder to be motivated to do such as task. 

21. How pushy does the dog need be to stop you from doing an activity or be able to redirect you to another activity?
Will the dog be persistent enough to wake you from a sleep when your blood sugars drop? Look at the persistence of the breed and what types of things they are persistent at.

22. How much support do you have to raise and train your service dog?
Do family embers believe you need a service dog and if so, are they willing to help? Do they have issues with specific breeds that would make them less likely to help?  

23. Can you get help for what you need to train? Or are you assertive enough to ask for help?
For example, if your dog is jumping up, are you confident enough to ask neighborhood kids to help your dog practice not jumping? Even if you don’t know them? Would you be able to ask strangers walking towards you to help you train your dog? Can you give them specific directions of what you need them to do?  

24. Is there a time frame involved?
For example, your current service dog is retiring or a family member is moving away. That may affect whether you get an adult or a pup.

25. Level of emotional sensitivity is needed from the dog?
Can the dog adjust his emotions to the level you need? (in other words, calm himself to calm you). Can he sense when you need this adjustment?  

26. Level of physical sensitivity is needed from the dog?
This includes impulse control for moving into a person’s space as well as how physically sensitive the dog is to physical touch. If your disability causes you to be physically rough with the dog will he be okay with that?  

27. Your fur-type and length preference.
There are different types of fur on dogs. The fur may matter if you are using the dog for emotional support and the physical sensation of long fur is needed. Or if you live in a wet environment, a shorter coat may be faster to dry. In a hot dry environment, a short coat with an undercoat may be preferable to protect the dog from sunburn.

“Guard hairs” are the outer hair that acts like a raincoat to protect the undercoat. The “undercoat” is the insulating layer near the skin that traps air and heat. These two come in a variety of combinations. Within the same breed, you may see different combinations of these so there is varying amounts of shedding. There are short-coated dogs, like labs. They are typically mostly a layer of thicker guard hairs with a lesser layer of undercoat. The guard hairs are shed regularly, to varying degrees. Some shed profusely. Single-coated dogs (those that have only mostly guard hairs tend to shed less. Their guard hairs are heavy and drop to the ground and stay there. They may pierce furniture and go right in. 12 years after my dachshund passed away, we were still finding her hairs coming out of couches and the seat of the car. Labs, Daschunds, German-Short-haired pointers, and Dalmatians have short coats. 

Longer coated breeds like Golden Retrievers shed mostly their undercoat. This fur balls up like cat hair and floats around the room and sticks to clothing. All of the longer-coated retrievers, German Shepherds, Newfoundlands, Great Pyrenees have this type of coat. 

Consider the color of furniture and clothing if you choose this coat type. White hair shows up on black etc.Some silky haired dogs have long fine guard hairs that shed little. Brittanys, Papillions 

Curly coated breeds like poodles have fur that is more like curly human hair but it gets caught on itself when it falls out by the follicle so usually only fall out when brushed. They need to be clipped regularly so add cost or effort on your part. Poodle (all sizes), Bichon Frise.  

Most of the spaniels have a thick undercoat that sheds but also need to be clipped regularly so you have both the shedding and the cost or effort of clipping.

Breeds like Welsh Terriers and Airedales have a harsh curly outer coat that does not shed. With the mixed-breeds, you can get new combinations of these coats. Another reason why you want to meet the dog in person. 

28. Is the smell of a dog going to be an issue?
The wet dog smell can be disagreeable to not only you but others you work with.  Some breeds have oilier coats than others. Pay attention to how each breed and dog smells as this may affect other people’s impression of your dog when working. Basset hounds, for example, have a very distinctive (and strong) odor. Once you’ve smelled it, you won’t forget it.  The breeds that need to be clipped may develop a distinctively doggy odor if not bathed regularly. Some dogs also vary their smell depending on what they are fed. Some dogs like Samoyeds have very little scent, even when wet. 

For some dogs, feeding raw decreases the odor (both from flatulence as well as general body odor). Also note that active dogs can develop odor through sweat glands on their feet. I knew of a mini daxie who had feet that smelled of bad body odor. This is because bacteria and fungus grow on the moist pads if they were not washed after hard exercise.  

29. Is your environment at home or work calm, scheduled or chaotic?
Most breeds and individuals do well with calm and scheduled but others enjoy some mental challenge as long as it is not all the time. Dogs that are intelligent and active like to have things mixed up at times to keep them interested. Hounds can do well in some chaos as they are so even-tempered if bait independent as a group. But all dogs need a break from it on a  daily basis.  

30. Are you quiet or loud?
Choosing a sensitive dog may not be a good choice if you are loud and boisterous as a person. A quiet person would not do well with a loud pushy dog.  

31. Do those around you have bias or prejudices for certain breeds?
Another thing to consider is to look at how the general public views the breed. This dog will be at your side in public and will affect how the public, managers, and co-workers interact with you.  One person noticed that people were much more friendly, helpful and tolerant of her needs after she retired her Belgian Malinois and got a yellow labrador. She felt they were uncomfortable with the Malinois as it was a protection breed. He was actually a very people social dog but people's perspectives do affect their interactions.

32. Do you like attention?
If you get an unusual looking breed or individual dog, you will be stopped frequently to be asked "What kind of dog is that?" which you may or may not be comfortable of have time to do. Introverts may not like this kind of attention so choose your dog accordingly. It helps to be prepared with a few prepared answers and how to remove yourself from the situation without being rude.  

33. Is there Breed Specific Legislation BSL in your city or region?
If you choose to use these breeds as a service dog, you need to follow the laws even if your dog is a service dog. Uneducated people will also show fear of your dog and may go out of their way to avoid your dog or conversely, educate you about local laws.  This can be stressful for both you and your dog. If you move into an area that has an outright ban on your breed, you could legally have your dog removed from you and even destroyed without your permission. Whether this is morally right or not is not the question. It can happen to anyone so it is brought up as a point of consideration here to prevent stress and heartache.  If you are willing to fight in in court that is up t you but that will add more stress and cost. 

34. What are your group or breed preferences?
A group is the kennel clubs way of classifying dogs that do similar jobs together. 
The 6 groups are: sporting hound working terriers herding non-sporting and toy (companion dogs).Breed preferences are which breeds of dogs do you like the best from what you know about them. Remember rather than looks, you want to focus on their general personally type and behaviors as this is the foundation of who they are and what they will be willing to do for you.

35. What personality could you live with?
Could you tolerate a goofy fun-loving personality or would a serious dog be a better match for you?  

36. Would you prefer a purebred or mix of breeds? 
Mixed breed puppies usually have an unknown genetic, gestation and socialization history. You won’t be able to test the dog for most health issues until he is 2 years of age. Considering an adult mixed breed dog may be a better choice as you can health test him and get to know his temperament before putting too much training in.  

37. Are you a dog person or cat person?
There are several breeds that are cat-like inbehavior. This typically means more independent. Daschunds and Shiba Inus are two such breeds.  Depending on the task you need them to do, they may work or not as a service dog. 

38. Do you have other things happening in your life that will compete with training a service dog?
All dogs, no matter the breed, need you to focus on their training daily during the first two years of life and beyond. The early training needs to be continuous, ideally with no breaks. Certainly the socialization period during the first 16 weeks of life cannot be set aside. Behavior and tasks training can be postponed but not indefinitely. You need to make a commitment to your dog to complete the training.  

39. How much time each day can you commit to socializing and training the puppy or dog?
At least 130 hours of specific training within 6 months is required by the Assistance Dog International (ADI). That is one hour a day 5 days a week for six months. Most dogs required 18 months to 2 years of training before their skills are solid enough in public to be considered a service dog.  

40. After all of this, how resilient are you?
Could you start again after a dog you have trained for many months is failing the process? Will you rehome the dog? To whom? Keep it? Can you realistically financially afford having two or more dogs? Do you have the time for the second dog? 

41. If you are using the dog for mobility support:
In general the dog must be at least half of your weight or heavier and at least 23 inches at the shoulder for small women and 25 inches at the shoulder or larger for men. Taller may be needed, depending on the fit of the harnesses with attached handles. Choose dogs that have a heavier bone structure. Remember that male dogs tend to be larger than females dogs so consider that. Larger dogs cost more in food, need more space, are at risk for more joint issues, have a shorter life and vet procedures often cost more. 

42. Can you travel to visit a potential litter or dog?
How far? This may limit the area that you can search for a dog in. Do you have a good chance to find what you are looking for? You may need to be more flexible in the breed or mix if the area is small. 

43. Can you travel to pick up the pup?
Ideally, you have been able to find one within a reasonable distance that you can visit a few times before bringing the pup home. But if not, some breeders will only allow you to adopt a dog if you are willing to come to their place to get the pup. Travel may include long drives in a vehicle, or plane trip with the pup in a bag at your feet in the cabin. Some breeders will ship a pup in cargo as long as the pup is accompanied by a person (doesn’t have to be you or a relative). Add this selection criterion if this is important to you. 

44. Do you prefer and adult or puppy?
With a puppy, you may not benefit for 10 months or more.  An adult may be able to start assisting you within a few months, depending on the tasks you need and how solid the public access of the adult dog already has.  Adopting a 5 to 14 month old adolescent dog is not recommended unless you can get an independent evaluation after the pup has lived in a home environment for at least a month (longer is better) due to being in the middle of a fear period. You have no way to know if fear you see if the dog’s fear is due to past experience, lack of socialization or is part of the dog’s temperament. 

45. Are you left-handed or right-handed?
This will affect the side your dog primarily works on. Studies have found that right-pawed dogs are twice as  successful as guide dogs. That is because they think predominately with their left brain which is in charge of jobs. They are bolder and inquisitive. Left pawed dogs tend to be more fearful since the right side of the brain is driven by fear. Use the "First-stepping test" to determine the predominant paw use. Record the first foot moved froward after the dog is standing with both front feet level. Take 50 recordings in about 20 minutes and you will have the answer. The more one paw is used, the more likely that paw is the dominant paw. 

46. What side will the dog work off most often?
If you are right-handed, you may want your dog to work off your left side. If that is the case, you will want your dog to have his left eye as his dominant eye since his right eye is mostly blocked by your body. To determine eye preference, place a patch over one eye and have the dog jump over a low jump. How well he does will vary depending on which eye he is using. The better he does, the more dominant the eye. Make sure the jump you use can be easily knocked over so the dog does not hurt himself if he miscalculates it. 

47. Which way does the fur whorl go on a dog you are considering?
Dogs with counter-clockwise hair whorl on their chest tend to be more confident dogs and are twice as successful as guide dogs. Dogs with clockwise whorls are more anxious. Assuming the experimentor is correct about the use of dogs on the right side of the handler, left-handled handlers may be better to choose a right-eyed dog and train them to work off their right (as in heel on the right). 

Link to the article with a video http://www.abc.net.au/catalyst/stories/3465535.htm