I agree w/ all these replys so far. Remember what it says at the bottom of my reply.make sure you have a consitant anchoring point. Mine is when I am at full draw my bow hand is open thumb and 1st fingure up like in hte shape of a "v" like I am pushing the bow away from me directly at the point of aim. (pick a small target). My release hand at full draw make a fist then draw your elbow straaight back and put the end of your thumb at the point on the back of you jaw. then I tell myself elbow out (meaning bow hand for me thats the left I'm right handed). anchor, aim small.
I also don't like shooting at my knocks because I go through too many arrows that way. spray paint small dots on your target then put a stick or something small to aim at in the middle of them. if you can hit each individual target in hte middle you are grouping and not ruining arrows.
Thats what I do! good luck w/ what ever your choices may be.