there are many organizations through which you can become a personal trainer, and you can find that here at IDEA http://www.ideafit.com/fitness-certifications.
Which one to choose is the most frequently asked question, and I would look for one that is NCCA accredited and nationally recognized. My recommendations are usually for ACE, NASM and ACSM. I am somewhat partial to NASM. They have developed a model for training called OPT which is re-iterated in every of their specialty certifications and thus creates a coherent unit.
The first thing you’ll want to do is determine in broad terms what kind of trainer you want to be and what type of setting you’ll want to work in. From there, you’ll want to find a certification that is accredited by the NCCA. The NCCA sets standards that these particular certifications must hold themselves to in order to ensure that our industry does not become watered down.
Once you’ve determined the what and where. Check the NCCA website for their list of accredited certifications. Personally, I think the best governing bodies to earn your certification through are NSCA and ACSM as they are largely the most difficult exams to pass, are very thorough, and each organization publishes their own peer-reviewed journal. That said, the difficulty of the exam certification doesn’t make a quality trainer. If you earn a certification through ACE, NASM, or NESTA (NCCA pending), and become a member of the NSCA or ACSM, you’ll still have access to all of their print and online publications which are unbelievable resources for continuing education. In addition, each certification from each organization comes with its own set of prerequisites.
In closing, ask yourself what your personal goals are as a coach or trainer, determine which certification you are qualified to earn based on your educational background or resume, and decide what kind of setting you want to work in. As long as you do your due diligence, you’ll be fine.
I hope this helps. Best of luck!
-Aaron Runner, MS, CSCS