As you progress through training your own service dog, you will find that there are behaviors that your dog does that you don't want to see and you just can't seem to over come. Once you reach that point, it is time to go back and figure out where the behavior started from and how you can change your dog's response to the situations. Retraining them sooner than later will help to smooth the training process for any behaviors and tasks that follow.

What Behaviors Should You Be Watching For?

The most problematic behaviors are any related to lack of impulse control:

grabbing from your hands (food or toys)
barking (especially when the dogs is demanding something) (might be a single bark or multiple barks)
slapping or grabbing with one paw
mouthing (you or visitors)
inability to stay still
dancing feet on platforms
spinning while waiting (for a ball to be thrown, or to go out a door etc)
pushy behaviors (at doorways, against legs, in your space uninvited etc)

What all of these behaviors have in common is that they are related to arousal level. When a pup or dog does not have or has not yet learned impulse control, these are the ways that it typically shows itself. 

To Solve the Problem:

1. Prevent the dog from practicing the unwanted behavior by managing the environment so he doesn't need to do the behavior. For example, how can you keep his arousal level lower? What can you do to prevent access to the physical triggers?
2. Break each unwanted behavior into smaller parts.
3. Identify what foundation skills your dog is missing.
4. Look at your own training mechanics. Timing, Rate of Reinforcement and Criterion are three common areas where most people need improvement to reduce your dog's frustration.
5. Control the physical and emotional environment you train your dog in. Dogs do respond to what's happening around them!
6. Retrain from the very early beginnings of the behavior in a new environment. Get reliable behavior and slowly increase the dog's arousal level. 
7. Video your training sessions and look at it with a critical eye or get someone else to do that. What are you doing or how is the environment set up to contribute to the behavior?
8.Teach impulse control generally (in other areas of life).
9. Get help from a professional. Set up a Skype or FaceTime session to make a detailed training plan, submit videos and get specific feedback on how to solve your training challenges.

Good luck!