at 30 yards, unless you're extremely high in the tree, or shooting a steep downhill angle, just aim where you want the arrow to hit. it's that simple. by all means, practice, but don't rack your brains and overanalyze it. it gets tricky when they are inside 10 yards. mostly because your bow will shoot high at 10 and 15 yards, and low at 5, and most guys mess up by not thinking about this.