Check out this video of Tim Lincecum warming up before throwing in a spring training game. Notice how flexible he is (obviously helps him throw as hard as he does)! Also, watch how he keeps his front shoulder closed until toe touch as well as how much he leads with his back/butt and stays coiled until launch position. Also, look at how long his stride is and how he uses his legs to generate violent rotational force.
BCM Performance Blog 