I load up my info in a ballistic calculator that will show me what yardage each hash on the reticule is. Then i play with the zero until i get it close to some thing like 300 400 500 on the cross hairs with a pretty much point and shot at 200. Or if its a rifle i plan to not have to shoot past a say 300 ill try and zero it so that I am in the kill zone from 0-300 when just aiming center of kill zone.