To be a fitness trainer, you must first be physically fit. You must serve as a role model for your clients. You are only required to have a high school diploma to work as a fitness trainer but many employers prefer to hire college graduates who have majored in a fitness or health-related field.This is especially true if you want to become a personal trainer who will work one-on-one with clients. Many employers require CPR, first aid and AED certification or, at least, training.Whether you want indicates that you have the skills needed to work in this occupation. Many, but not all employers require this credential, but you will be a more competitive job candidate if you have it. You should take great care in choosing the organization from which to get your certification.t to work as a personal trainer or instruct students in group classes, it is a good idea to get professional certification.