Choosing a personal trainer can be difficult. A lot of times you sign up at a gym and a trainer gets assigned to you and you are stuck. Most of the time you won't know what to look for anyway
1. The trainer has a proven method.
Every trainer is going to stick with a few methods for training. There are many ways to train that can give you great results. The thing to avoid is the trainer that isn't interested in your goals. They just want to train you their special proven way.
Some trainers are going to train specific demographics and have spent time developing a system that has great results for that demographic. But be weary of trainer that trains every client the same no matter the demographic. If that is what you want, join a group training system like Crossfit, boot camp, Zumba, or something else that interests you.
2. The trainer doesn't listen, or ask you a lot of questions.
The whole point of personal training is to have a workout tailored to you. That first meeting should include a game of 50 questions. The trainer should listen and ask follow up questions. This kind of fits with the above. The time should be focused on you. Yes, the trainer needs to sell themselves and should explain their qualifications to you. But it should be all about you.
3. Education and certifications.
Not every good trainer went to college for exercise physiology. But if you find one that did, all the better. Find a trainer that has a reputable certification. I know you don't want to delve into the land of understanding personal training certifications. But ask about their certification, google it. Make sure it isn't the easiest cheapest mail in certification out there.
Your trainer needs to know their anatomy. They need to know how the body works and how to prevent injury. They also need to know how to get results.
4. The know-it-all.
Ok, I will be honest here. All of us trainers are going to, on some level, think we are the best trainer around. It is just part of what is necessary to compel people to change their lives for better fitness. We need a confidence that doesn't make our clients question our abilities. We need our clients to put their trust in us.
Let's go back to #2. Listening. Your trainer shouldn't be above listening, researching, asking peers, or calling medical professionals. I have found that the overly confident trainer is usually recently out of school. They haven't discovered yet how much they don't know. College graduates are armed with the latest research knowledge, which is a great thing. But there is so much to learn still, always. It is important to understand that as a trainer.
5. The trainer who doesn't like to train your kind.
There are a lot of trainers out there that will focus in on a demographic (as I mentioned earlier). There is nothing wrong with that. But don't hire that trainer if you aren't their demographic. Generally people fall into one or two of several categories:
Weight loss
Athlete
Special Populations: injuries, illness'
Youth
Some trainers find no joy in certain demographics. Weight loss clients take something special because it can be an emotional journey. It takes and athlete to know one. Youth takes a lot of experience because their abilities are extremely different than adults. Special populations takes patience and the reward of success is different than the others.
Find a trainer that wants to train you. They need to love you for who you are and where you are at and where you are hoping to go.