Whether you are planning on working for a gym, at a studio in your home, or in a clients home, the most important legal concern for a personal trainer is protecting ones self from potential liability. This can be done in a multitude of different ways. Her are some of the more important ones.
First off, do the proper research and choose a reputable company in which to pursue a personal trainer's certificate. Complete the required course studies to the best of your abilities. Once you have successfully completed your training, your next step is to purchase liability insurance from a company of sound reputation. This is not only to protect you, but your client as well.
Secondly, never attempt to diagnose, treat or cure a client's medical condition. I currently work in a gym and make it clear to the patrons I am not a personal trainer, yet I still am asked daily for advise on which exercises I would suggest for a multitude of ailments. I advise them, even if I were certified; I can't and won't give them medical advice. I advise them to make an appointment with his or her doctor to discuss any limitations or restrictions he or she might have. If as a personal trainer, a client does suffer an injury under your tutelage, make a detailed report of the incident for your own records in case they are needed in the future. .
Third, it is always a good idea to complete a CPR and first aid course. This will not only help protect you from financial or legal liability, but more importantly to help protect the client. .
Make sure you are properly trained in the routines and techniques you are teaching your clients. Also, never over exaggerate your abilities or the amount of experience you have in the field of personal training. This will help to reduce the risk of injury which will in turn reduce the risk of liability. .
Next, if you plan on going into business for yourself, make sure you always have current permits and business licenses.