Learn "THE SECRET".
Many moons ago, when I went to the original Yankee Stadium, I watched the Big Three---Raschi, Reynolds and Lopat---and I saw what they were doing and how they were doing it. They were driving off the lower half of the body, all three of them, using the legs, the hips and the torso in one continuous---and, it seemed to me, seamless---motion, creating a flow of energy all the way up through the shoulders and arms, thus generating more power behind their pitches (and taking a lot of pressure off said arms and shoulders). I made a note of what they were doing, and I started working on it on my own, and as I practiced this essential element of good mechanics I found that I was doing exactly what those three pitchers were doing! It helped that I was a natural sidearmer who could and did throw hard and used the slide-step, and I discovered that I was getting extra speed and power in my delivery.
A good place to begin is the "Hershiser" drill, which aims at getting the hips fully involved. It requires no special equipment, just a fence or a wall, and as you work on it and master it you'll find yourself translating it into your overall motion. :baseballpitcher: