I will have to agree with Shawn, a hand on experience is the best tool they could acquire while still attending college. Since most of them are probably new to the industry with no previous experience in training and/or interacting with clients, they need to engage into some type of a program that will give them first-hand experience in these areas. An internship is a good place to start where they will have to demonstrate their abilities as a trainer and also can be mentored by a more experienced trainer so they can learn.
Text books and passing a test are great, but not enough when it comes to interacting with different personalities of clients and individual needs. Also being a trainer is more than just coming up with an exercise plan, he/she has to be a motivator, a great listener and at the end an entrepreneur as well if he or she wants to be successful.