It's a skill that's good to have, but hopefully you won't ever have to use it. No one wants a fist flying towards them. But just in case you find yourself squaring off with an angry guy who won't use his words, here's how to properly block a punch, according to defense expert Tony Blauer. He's the creator of the S.P.E.A.R. System, which relies on your body's natural startle/flinch mechanism to help you successfully defend yourself.