As usual, Al is right on the money. If you read Tony Boyer's book, he takes it a step farther. He centers the crosshairs in the scope by running the adjustments from stop to stop then backs off half way. This gets the erector tube in the middle of it's adjustment range. He sets his rifle on a rest with the bore sighted on target. He then will shim the scope as needed to get the scope aligned with the target. With shims in place he then will bed the scope in the rings.
-Al