you need to get out and shoot it at all the ranges you anticipate shooting out to. then, determine the ballistics, and then decide how much hold-under you can live w/ at closer ranges, and how much hold-over you can handle at further ranges.
on my precision rifles, i twist turrets - so i am zeroed at every range +/- 25 yards (my turrets are marked in 50 yard increments).
on big game hunting rifles, they are all zeroed for 250 yards.