Start: Grab a relatively light bar with a full overhand grip that's a bit wider than shoulder width. Stand and hold it at your chest with your elbows out to the sides and your knuckles pointing straight ahead-from the waist up, you should look like you're about to do a bench press, except you're vertical instead of horizontal.
Finish: Explosively press the bar forward until your arms are straight in front of you. Do this without letting the bar dip down. Quickly pull it back and repeat. Work hard but keep the bar under control-don't slam it off your chest.