"Deception," my pitching coach told me a long time ago. "A lot of what I do on the mound is just that---deception. Let me tell you a few things about it."
And he told me. He talked about allowing a batter to think you're going to throw one pitch and then coming in with another. For instance: Most batters have a particular mind-set when they come to the plate. They're thinking fast ball. They set themselves for a fast ball. So what do a lot of pitchers do? They throw a fast ball, often down the pipe, and the batter goes after it. Wham! off the wall for a double, at the very least. Wrong move. Give them a good breaking pitch---something like a knuckle-curve, which is notoriously difficult to hit, and your first pitch is strike one.
He talked about pitching "backwards"---starting off with the breaking stuff, getting an 0-2 or 1-2 count, then jamming them with a fast ball. Well---I didn't have a fast ball to speak of, but I had some pretty hard stuff, and I could use that. He talked about moving the ball around---high, low, inside, outside---and changing speeds (and he had to tell some pitchers he was working with more than once!). And he spoke of what they call nowadays "pitching to contact", which is just another way of saying "get the ball over the plate and make the batters hit it---make them go after YOUR pitch, what you want them to hit."
And I listened, and I put all that into practice. And I got a lot of outs.