I always setup my guns to shoot the center sight picture. If they have fixed sights, I will purchase and install the rear sight of choice first (generally a blacked out competition style serrated sight). Then go shoot the gun with the ammo I plan on shooting (124gr most likely) and get the impact shift. I then purchase the right front sight (generally a fiber optic) to correct the point of aim to match the point of impact. This is all assuming you don't want to install an adjustable rear sight.
I zero all my competition guns at 25yds standing freestyle (unsupported). I expect a sub 3 inch group when shooting for accuracy, so I don't have stringent standards.
Cheers,
Toby