This one will be pretty easy for anyone who's already mastered palming a coin, but it highlights two other areas that are vital for budding magicians: acting and coordination. Performing magic is more than just knowing the method - you also have to sell the effect to an audience. Making your movements fluid and natural takes a lot of practice, and this trick is simple enough to let you focus on those elements. Shout out to Matt Wayne's use of the term "thumb crotch," as well.