Here's an awesome technique to save Action Points (AP) used in VATS. If you're feeling confident when fighting an enemy or group of enemies, simply aim at an enemy in VATS, but don't fire. You'll retain your AP but still be aiming at the part of the enemy's body in question that you were in VATS. If you shoot quickly enough, you should still strike the desired area without having to expend any AP whatsoever.