- Challenge them a bit. Don't try to "one up" them - if they know what they're talking about, then the odds are good they are going to know more than you do (they should, anyway). But they should be confident and consistent in their answers.
- Tell them your goals, and ask them how they would help you get there. Be careful of anyone who seems too quick to simply answer what they think you want to hear - in fact, I would rather have someone tell me "I'm sorry, I don't think that's possible" than have someone who simply flips around what they're willing to say in order to make the sale. You want a coach, not a "yes man".
- Ask them what they last did for continuing education, and when they did it. If they haven't taken a course in the last half year, then staying current with what's happening in the training world is clearly not high on their list of priorities. A trainer who was at the top of their game 10 years ago and has taken one continuing education course since then is far from up to date (similarly to checking their certifications - be careful if all they can offer you is internally-run courses).
- Set up a complimentary session with them. Every good trainer/coach should be willing to offer you a chance to try their service - if not, you probably don't want to work with them.
- Finally, ask yourself - do they inspire you? Do you walk in and think "That's someone I could use as a role model"? Because if not - if they look like they're having their own struggles with maintaining an active lifestyle, for example - then how can you expect them to lead you to your own goals? If nothing else - listen to your intuition.
Next week - assessing the initial session.