Even with a great cert they can be a shit trainer.
Being a good trainer also has a lot to do with how the person interacts and listens to their clients.

I've hired more trainers than most anyone I know and believe me the look, cert and experience matter very, very little in the long run.
They either have it or they dont.

how do you pick a good one - well just talk to them and see how they would train YOU - if you are comfortable with what they say and their methodology then give it a try.
If it doesn't work out 99.999% of the time you can chnage trainers with little to no problem.
If you hire an independent - then ask for 2-3 free sessions first.
If they're worth their weight in mud they'll be willing to give you that and let you find out for yourself.


Sal