If using a scope and you have a good solid rest, take a shot at the bulls eye. Now without moving the rifle, hold a steady aim on the bulls eye and adjust the cross hairs so that you are sighted in on the bullet hole from the first shot and you should be dead on regardless of distance. Of course it helps if you bore sight first so that you are on the paper with the first shot.
http://www.youtube.com/watch?v=TiOpQY2ORo4