Ah, this is the biggest question of all!  You become a better instructor each time you practice the Pilates work in your own body but this doesn't mean you have to fork out a lot more money!  From doing a video to taking a class to just working out on your own, Personal Practice hours are vital to understanding Pilates.  Student teaching can range from grabbing your best friend, parent or spouse and teaching them what you are learning, to volunteering in a school or for a non-profit.  Practicing the words and the work make you a better teacher.  Observation of other experienced instructors is vital to shaping your Instructor personality.  Watch and see what works, what doesn't and how another instructor’s words help their clients succeed.