If there's a single, overriding, all-encompassing Golden Rule of pitching, it's this: Never be predictable. This supersedes every other rule, strategy, guideline or piece of advice. For instance, you never want to throw a ball as the first pitch of an at-bat, but you definitely don't want to throw a fastball every single time either. Batters will sniff out a pattern like that and know what to swing at before you ever start your windup. Don't alternate pitches either (fastball, curveball, fastball, curveball). Your advantage in the pitcher/batter showdown lies in the batter's uncertainty. You've got to keep him guessing.
There's a specific pitch that perfectly exemplifies this strategy – the changeup. A changeup is a pitch that looks just like a fastball from the windup through the release, but it's about 15 to 20 miles (24 to 32 kilometers) per hour slower. It's accomplished by making a small mechanical adjustment to the throw, like reducing the stride, not pushing off the rubber as hard, or holding the ball with an extra finger to increase friction [source: Schlossberg]. The point of the changeup is not that it's a 75 mile (120-kilometer) per hour pitch; it's that the batter is expecting a 90 mile (185-kilometer) per hour pitch. That's a huge part of pitching strategy – set the batter up to think you'll do one thing, then do something else.