The way I just heard it explained to me was to lift your glove side leg while still maintaining balance-then (the experts can argue this fact),as you fall forward or push off with your back leg-this is the time to begin to lead with your hip. The key here is to not do it immediately while you are lifting your leg-you must gain the balance first.
While watching my son getting lessons on this-the coach asked him repeatedly to lift his leg-and hold it while keeping his balance. Then once the leg was lifted to the proper level and balance was there, he would tell him to go and we would stick his hip out and then begin the delivery forward and throw. (This is more of a muscle memory trick than anything else). Without sticking this hip out-it resists your lower body from getting into the momentum building process entirely-thus limiting your velocity.
The balance point in the entire delivery is only a split second-so don't lift and hold too long or stop the delivery motion or then you'll get all screwed up.
Hope this helps-good luck to you.