Make certain that you're shifted over your front leg (to some extent) before attempting to throw a left uppercut - afterwards, your body will be positioned to follow the left uppercut with either a straight right or a right hook - FLOW is key here - a left uppercut flows nicely behind either a straight right or a right hook - while throwing it, "tork" your body by turning your chest to the sky - this twisting motion not only allows you to get everything behind the left uppercut, but it also allows you to cock your body for a follow-up right hand.