I definately like to have my windage centered when mounting a scope and go to great detail to get my mounts adjusted to allow for a perfect centered reticle when mounted. As for the elevation, some of my rigs are set up to be at the bottom of the adjustment when shooting at one hundred yards.
The mirror trick works well on most scopes. Maybe it is my eyes, but high power scopes with target hairs are a problem. I have to resort to counting clicks.
