scott is right about a quick, smooth release. however to build on what puma said,,,> I read a good way to tell if you are over bowed or under bowed is if you can hold at full draw for about 10 seconds. (dont confuse this with shooting, though one day you might need a 'hold' as the animal is stepping into position)
after a 10 second hold, you can either let the bow down, or let an arrow fly)
For me, the arrow is gone a wink after I get to anchor, but I found some 'practise' shots with some long 'holds' really helped my shooting; by spending this time on muscle memory.
A few times a week I shoot some arrows with a 10 second hold. It's fun. It's hard to explain, but since I began this drill I can now feel my form better on the normal quick releases...