This method works for me -- I take the the index finger of my left hand and bend it slightly to for a "C." This is then placed over the arrow, with some downward pressure (my force scale is broken, so I'm guessing about 0.10 pounds of pressure?). When I'm ready for my shot, I straighten out said index finger, and then bring it back inline with my other fingers (on the bow handle). It's effective and cheap (just look around, most of us come with index fingers). If you're a left handed shooter, do the same but with opposite fingers, and your index finger will bend to look like a backwards "C."
In all seriousness -- great info here. You guys that use the rubber bands, when they fly off are you worried about any noise they make when they hit leaves or branches? I might have to try this out.