I think that taking some anatomy courses and whatever related courses you can take at a local college would be great, it depends on how far you want to take this. Some colleges have their own personal training degrees or programs that can fill in the gaps left by a lot of the national organizations.

There are many national certification organizations out there, the three top ones are ACSM, NSCA, and NASM. I am certified by NASM. That takes mostly independant study and some live workshops, and an examination.

Hello,
If you are not already certified by now...
Besides getting certified or educated by the NSCA or NASM, because they are both highly respected, you should spend time watching or assisting very experienced trainers in a health club. Although the certifications are important, it is extremely useful to see the exercises performed and an organized workout over and over again. By the time you become certified you'll have a good odea of the job and you'll have accumulated more knowledge. It's the same idea asn having chemistry class and having checmistry lab. You need the practical and book knowledge to safely train people.
Best of luck!
Karen
www.GymnasticsStuff.com