What Makes a Good Exercise Instructor?

As a fitness instructor and owner of a local fitness studio, this question of what makes a good instructor is always on the back of my mind because it seems to me, it's what keeps people coming back. The most important thing for me is that my clients get a good, appropriate for them workout and that they have a good experience, walking away with a smile on their face. I get a lot of "I hate you," looks, deer caught in the head lights stares of eminent doom during the workout, but ultimately I would say 99.9% leave with a sense of accomplishment and feeling good about the whole experience- at least that is what I strive for. 

In my seven years of instructing, I have learned a lot along the way and have found that a good instructor is more than being nationally certified, CPR and first aide trained, and keeping certifications current, or even knowing the mechanics of movement, the safe and effective exercises to perform and keeping up-to-date on the latest physical fitness and health related research. Good instructors not only impart their knowledge, they give of themselves. I truly believe the best instructors are the ones that get up and pour their hearts out, caring about each and every person that comes to their class each and every time. It's the same thing that you would want from a good school teacher- someone who not only knows the material and how to teach it, but LOVES the kids most of all. 

I'd love to hear from you. What do you think makes a good instructor?