Get a good level bow, (Skorms' Bow, Master Bow) and go to an area where there's a good enemy that won't notice your presense easily. (Arena with Rock Trolls, Bandits) Draw back your bow to full strength, then wait for atleast 3 minutes or more, then fire. This'll only get you 6 skill points if you hit the target, but you'll get around a 43-70x combat multiplier. Quickly collect the exp orbs on the ground, then rinse and repeat, or go to the Demon Door outside the Hobbe Cave.