One to Two Inches High at a 100
When sighting in a rifle with only a 100 yard range a good rule of thumb is to put it one to two inches above the point of aim at 100 yards. 2" high for slower non-magnum cartridges and closer to 1" for magnum cartridges. For most cartridges this will keep the bullet in an 8" kill zone until roughly 250 yards, further for faster/flatter cartridges. Your mileage will vary, but for most cartridges this rule of thumb works well.