Given the interest we had in this topic last year, I thought you might find this post on reading the quarterback worth a look, particularly this part:
… The solution is to read the QB’s non-throwing arm. Teaching the FS (or any other pure zone dropper) to read the long-arm is an effective technique. The FS should break when he sees the QB’s arm go long (or lengthen). The typical QB does not pump-fake with his off arm extended. The only active arm in a pump fake is the throwing arm (unless the QB pump-fakes with both hands on the ball, still there is no long arm in this type of fake). The long-arm is the motion a QB makes when his off hand creates separation from his body. This separation happens in the beginning stages of a QB’s throwing motion. Have you ever tried throwing the ball with your off hand stuck on your body? Try it sometime, it is pretty difficult. Have you ever tried pump-faking with your off arm extended, its possible but it will throw off your throwing rhythm. Most QB’s do not have the adequate time nor patience to develop this type of pump fake.