I have my 270 sighted in aproximately 2.5 inches high at 100 yards and that allows me to be no more than +-3 inches to 300 yards. Stalking bear is talking about the same method of sighting in but he is giving a little more than 3 inches above or below point of aim. I just personally like to use 3 inches above or below point of aim.

I sight in all my rifles this way. +-3 inches.