The difference between a great trainer and a good trainer is rather simple:
1. S/he can look into your eyes and say, "I don't have to do this, I want to do this." And you know s/he means it.
2. S/he has the desire to help you without conditions.
3. S/he knows your limits and pushes you just past them every single time.
4. And lastly, s/he does not use high pressure sales tactics for things you do not need to increase how much s/he earns on commission or for a promotion.