Yeah silver hit the nail on the head, dont dive into ACSM NSCA or AFAA. go with a cert thats more basic an not as costly, see if you can get in at a gym or an apprentice at a studio, if you like it, go for the bigger name ones. I'll be completly honest with you though up front, i got a few certs that are easily recognizable, and i to this date have never had someone ask to see my cert, i have to waive them aroun to showcase my credibility lol. thats my next issue. do not pick a cert becuase all your gym buddies and trainer friends thinks its cool, find one that provides quality information and goes deep into the theory of exercise perscription, and program design. personally i get crtified by a couple companies, and i just pick up the books colleges use in exercise science courses. good luck either way man, this can be a really rewarding career, but it can also be a nightmare if you go about it wrong!