Since I teach at a resort spa, I often train guests who have personal trainers at home. Some of them have been seeing the same trainer for years, and for the most part the trainers appear to be good from the quality of their clients form. But every once in a while I hear horror stories that make me advise, "Fire your trainer!" This is your body, your money, and your time.
Fire your trainer if:
when you say an exercise hurts you she tells you to stop whining
he comes to a session stoned, drunk, or hungover
he tries to sell you the best acne treatment
you're in neck or back pain that is getting worse instead of better
you have been injured in a session with that trainer