Start with the essentials and learn the proper technique for passing overhand.  So many players begin playing without the proper instruction and end up learning to throw with a sidearm or angled throwing motion.  After only a year or two of using the incorrect form a player can seriously stunt their lacrosse potential by building muscle memory of an inaccurate style.  Passing overhand is universally harped on by coaches because it is one of the the most important and fundamental skills built during a players first few years.  After developing an overhand throwing motion learning to pass at other angles becomes a tool rather than an impediment.