'I'm gonna have to go against the "just shoot" mentality. I've seen a whole lot of primitive archers that couldn't hardly shoot the side of a 5 gallon bucket at 10 yards let alone pick a spot and drill it. The whole thing boils down to repeatability of your form.
Now theres nothing wrong with doing it your own way as far as anchor points and how you hold yer bow and stuff like that, although some are better than others for certain kinds of bows. But there are a few things you need to get imbedded in yer brain like Pat said. Your anchor needs to be there EVERY TIME or your gonna be inconsistent, whether its at the corner of your mouth or under your pectoral muscle, same every time. Keeping your bow arm still through the shot will improve your shooting, having a dead release(non moving ) is good , Keeping the bow arm, shoulders and the upper arm of your drawing arm in a straight line helps as well. Now all these things , any shooting form, even bad ones, have to be learned.
I had to break down my form last spring and build it back from scratch. I'd developed some really bad habits. I was having accuracy issues at 20 yards, not good. I did alot of shooting from 10 yards at a blank haybale. Just concentrating on feeling my anchor and how I was doing everything til I got it ingrained again.
Oh yeah the big one , "PICK A SPOT"
It helps to have the properly spined arrows for your bow as well. I've seen folks fighting to hit a target with underspined arrows and its hard.