I don't shoot groups anymore. I can't believe how much I improved when I quit group shooting, and now shoot only one arrow at a time. I go up and get it, and go back to random spots yardage unknown, and shoot again. Its either a hit or a miss.
I have a morrell bag with lung and heart on one side and just roam aroud the yard and shoot.....then I do the same with my 3-D's..
Used to tie a ballon behind my Nitro RC trk untill I hit the trk [:@],that cost me 180 bucks to fix....But it was fun.
Not to shabby Bob-co, but I agree with Big Country. I do shoot 2 at a time, but never at the same spot. I cover my target with a big black plastic bag. I just pick a previous hole to aim at and try to concentrate on it until the arrow hits. If I loose my concentration, I dont have any idea what I was aiming at. I dont use bullseyes or targets anymore. might sound dumb, but works for me.