If you're consistently right or consistently left then I would suggest moving your rest in small increments, etc as nub mentioned. However if you're off in both directions then it's probably from hand torque, poor form, or maybe fletching contact. I was having a similar problem earlier this summer. My groups were consistently 4 or 5 inches to the right. I thought that it was hand torque and drove myself nuts trying to perfect my form. Then I read some posts here that suggested going to the Easton web site and downloading their tuning manual. I started at the beginning of the manual and worked my way through. I found out that the arrows I was shooting were under spined. Some new arrows and a few minor adjustments learned from the manual and now I've got my field points and broadheads grouping together under 2" at 20 yards. Check out the Easton site.