I just read an article on the one shot -- two person sight-in. Put your gun on sand bags and aim at the bull' s eye. Shoot, get settled, and aim at the bull' s eye again. Hold the gun completely still and direct a helper to adjust the scope until the cross hairs are on the previous bullet hole. The gun now shoots wherever you point it!
[X(]The only way to screw this up is to allow the gun to move or wiggle while the helper is adjusting the scope.