Depends on what you want to do. ACE or NASM are good basic certs. NSCA IF YOU WANT MORE sports conditioning. ACSM is a winner. Being a PT and a former Regional Fitness Director for a large Health Club chain, I recommend checking out PTA Global. They have the most common sense approach and practical learning that is immediately applicable. NESTA and NCCPT are still NCCA accredited but are also less expensive.