There are several ways to get your personal trainer certification. You could do a Bachelor's degree in Exercise Science, Exercise Physiology, or something alike.
But you do not really need it, if you want to be a personal trainer (Bachelor's degree is really an overkill for that goal).
You could get a certification from any organization, accredited by NCCA (National Commission for Certifying Agencies).
One important thing to remember, is that you do not need to be a bodybuilder / power-lifter yourself. Of course, you still are a role model for your clients, so be healthy, and eat healthy – but there is no need for huge biceps and triceps.
After you choose your certification, and finished with the education, you can move on to the next stages.
A good personal trainer will also extend his knowledge to some niche. For example, you could specialize in bodybuilding / power-lifting / fitness / health. If you have more advanced knowledge in, say, bodybuilding niche (which does have own own secrets) – of course, your value, as a personal trainer, will be much higher.
Next stage is considering to take first-aid (or a CPR) course. You might not need it, but a client will prefer a trainer with some medical background, that could be used in case of emergency.
Decide what you want to do.
You should weigh your pros and cons, and see whether you want to be a trainer in the gym or start your own private trainer business (In this case, you will need some business advice, like what forms to fill, and so on). Decide, whether you want to start in a small gym or a large one.
A personal liability insurance.
You should definitely research more about it, and get one yourself.Find more information / e-books, explaining about this matter, which can become very serious.
Decide how much you will charge.
This might sound a little strange, but if you think about it for a moment – setting your price tag is not a trivial thing at all. Should you charge $ 15 or $ 50? Should you charge more than other trainers, less, or the same? Usually, personal trainers charge between $ 15 to $ 70 in gyms, and between $ 25 to $ 200 (per hour), while being independent.
Now, that you're your own boss, you have to find a job for yourself.
One possibility is to ask friends and relatives, whether they need your services, and another good option is to find local gyms. It is always a good idea for a beginner, to work in a gym, for an experience. Every job has its own nuances, and you want to know most of them, before going out there alone.
Constantly keep improving yourself.
There is always something new to learn. While the experience, that you'll be getting will play an important role in your education, you have always to find new information, shared experience, new theories and so on. Internet is an excellent place for this purpose. Find forums, articles, exchange your thoughts and stories with other personal trainers. Keep learning – this will increase your value as a trainer.
Be a role model.
As we have already said, you are going to be a role model for your clients. While this does not require you to be a strong and big person, you do need to influence people you work with. Most of the times, person you are working with, does not really know what he / she wants. You have to suggest, understand, and go on with your decision. You have to be authoritative. Your voice timbre and volume, your interaction with client – all should suggest, that you know what you are doing – otherwise clients will leave you.
It is mostly important not to give in to human weaknesses. Sometimes people tend to give up, and it is personal trainer's job to keep them from it.