Trainers should obviously know the proper movements to target major muscle groups, but no matter how knowledgeable a trainer is, the prospective client needs to ask some very important questions.
Personal trainer Mike Donavanik says the first thing you should ask is what credentials they have, so you know that they're certified and well educated. And don't just ask, make them show you their credentials -- all good organizations issue cards with expiration dates.
Along with credentials, you should also ask for client references.
"You need to be able to make a call to the person's former clients or their current clients and know that the person is happy with their trainer and getting results," said trainer Jill Brown.
You should also talk to potential trainers about their accountability and recommended exercise routines.
"I would want to know how much you could push me; if I'm going to get a good work out every single time; if you're going to be accountable; if you're going to show up; and if you're actually going to be happy," said Donavanik.
But one of the biggest things to think about when choosing a personal trainer is compatibility. You need to trust that person and feel at ease with their style and personality.
"When your trainer is going to be up close and personal with you and touching you and making suggestions on your form and literally assessing your body fat and looking at all your little secrets that you're trying to change, you need to feel comfortable with that person," said Brown.
Finally, Donavanik says make sure you have some kind of contract, especially if you're using an independent trainer and not going to a fitness club.
"One, to protect yourself, and then also to make sure that the trainer is held accountable. So you know, if you sustain an injury, God forbid, that you're protected and that you know that your trainer has insurance," he said.
In order to find the best trainers, one gym owner holds trainer turnouts to check out who has all the right moves.
"We generally hire about one person out of the 30 that we see," said David Barton, owner of David Barton gyms. "We're weeding them out in big groups."