Hiring a trainer or coach can be one of the best investments you make. A good trainer can literally help you live longer, avoid injury, and realize goals you never thought possible.

However, a bad trainer can be a waste of money, pump your head full of nonsense, and even cause you injury. A good trainer is worth her weight in gold, but how can you make sure you’re getting what you pay for?

The first time I did a free trial session with a personal trainer, I worked harder in that one hour than I ever had on my own. It intrigued me. Exercise, to me, had always been pretty much the same: cardio first, then some weight machines in a circuit; but a workout that involved barbells? Jumping? Speed ladders? I didn’t know what that equipment was for the most part, but I also didn’t have anyway of knowing if my coach was an effective trainer or not.

Now that I’ve become a trainer myself, I’ve determined that the best trainers tend to share a list of common traits.

Here are five criteria that can help you hire the right coach or trainer to get you to your goals:

1. They do a thorough assessment. You can’t design a program for someone without knowing anything about that person. Good trainers will take you through an initial assessment process and ask detailed questions about your physical history including injuries, pregnancies, and aches and pains. They will put you through a baseline movement analysis, and determine the program best suited for you, based on your abilities and goals.

2. They have a plan. A fellow coach put it this way: “The client picks the goals, but the coach picks the methods.” If you are hiring someone for their expertise, you have to trust in their plan. Trust is built over time, but initially they should give you a realistic idea of what it takes to reach your goals and explain the requirements. They should address your expectations clearly. A good trainer will be open about their methods and not claim to have a special “secret” to fitness that others don’t. The only way to fat loss and muscle gain is consistent, hard work.

3. They’ve done their research. A good trainer bases the principles of their training on relevant scientific evidence and is able to back up their claims with appropriate research. They should also have knowledge of other credible experts to which they can refer you, should you require a massage therapist, physical therapist, or dietician in order to achieve your goals.

4. They’re experienced and qualified. This is a bit more of a delicate point, because not every trainer has formal degrees and a laundry list of titles after their name. Impressive qualifications don’t always mean they are good at what they do, so balance this with the ones above. Look at who they work with (are their clients people like you?), what they write (many have online blogs, Facebook pages or personal websites) and ask about their background. A good trainer will never take offense to you doing your research.

5. They take a holistic approach. The best trainers see more than just your body and know that the time you spend with them is only a small percentage of your life. They will go out of their way to educate you on everything that makes a difference to your health such as adequate sleep and relaxation, proper nutrition and allowing recovery from training.

Hiring a trainer is like any other investment or large purchase—your best bet is to be an informed customer!