josephmovie saidLook for some who is:
1) Around your age
2) Trains people who get results. Keep an eye on people at the gym and see who is being trained and seeing changes
3) Someone who actually likes you. Can't really sort that one out until you've trained together a bit.
As a PT I agree that there is a lot of turnover, but also it is not fair to those good PTs with #2) above because results are often dependent on client adherence to diet. You can train them, but you can't put the right food in their mouth at the right time. I have a client that is losing progress because he is infrequent with his sessions (like if we meet once a week and he skips out on 2-3 weeks at a time, it's like starting over). He also is "in one ear and out the other" about me trying to get him to eat more calories (and I've beat the dead horse with educational material and counseling).
And yes, if they aren't paying attention to you, they aren't doing their job.
Keep in mind that certifications are nothing but red tape. I'm NASM'd but compared to having degrees in the field, a certification is a joke (you just take a test pass or fail with no hint on what you missed, pay the money--prep time dependent on how much kinesiology you know already). Gyms value certifications more than degrees probably because they get sponsorships from certifying bodies for hiring those trainers.
Some certifications are better than others (NASM, ASCM, NSCA, which also puts out the CSCS credential, the only one that requires a bachelor's). ACE is widely accepted even though it's inferior. NASM is into teaching stability exercises and is better for someone who just started out exercising, but they also do a lot of "interesting" stuff like "foam rolling/myofascial release," which is something I never learned about in the 9 years of formal time I was in school for (BS Kinesiology, M.Ed. Clinical Exercise Physiology). I don't think it does anything other than being a self massage, which just feel good to my knowledge (and I've interned with chiropractic and physical therapists). Experience working with a client with similar issues helps also, but even if they have experience doesn't mean they are doing the right stuff for it--hence education being important.
Also regarding doing the same workouts with different clients--if the goals are the same and they are at the same level of fitness, why NOT? Furthermore, doing the same workout from workout to workout is called progressive resistance training, which builds muscle (assuming you are adding weight). Muscle confusion is something the CrossFit marketing cult has tainted our society with such that people are genuinely confused about basic principles of physiology.
Don't hire a crossfit trainer. It's not a recognized certification among those with real fitness credentials.
That said, I sometimes will do agility workouts outside with some clients whose goal is purely to burn calories (ie so they can eat more food). I'm not going to do a high calorie burn workout with a client who doesn't eat, and I struggle to get food in him at all. My goal in that case is low volume workouts, the same workout every week. I do what is effective rather than what is expected, and when the client thinks he knows more than me or doesn't think I know what I'm doing (and I can give sound explanations), then you need to go find a trainer that does what you expect (even if it isn't the right thing for your goals). I find it frustrating when a client does not communicate that he/she is unsatisfied even when asked and questions the efficacy of a workout just because "other people are doing X workouts [which are for different goals or sponsored by some new fitness fad such as crossfit or P90x]."
I also find it frustrating when a client doesn't admit to muscle soreness and injures themselves. That's your own fault for lying to the trainer. If a muscle is sore, don't work that muscle until it heals. Simple. Stop trying to be macho. I get sore myself, and I take time off.