The fast ball is the most important pitch in baseball. It's important for all pitchers to learn how to master this pitch before moving on to other pitches.
When throwing a fast ball, pitchers can employ a four seam fast ball grip, where their fingers lay across four different seams on the baseball. This will be the straightest and fastest pitch they throw. The other type of fastball grip is the two seam fast ball, where their fingers lay across two seams. And this pitch will run down and in. A right-handed pitcher will throw this ball. It will sink down and in to a right-handed batter. As opposed to the four seam fastball, which is the fastest pitch thrown and the straightest.
Another fast ball is the cut fast ball, which is a combination slider and four seam fast ball, where the ball will cut away from a batter. Fast balls are thrown when pitchers are typically behind in the count, such as 2-0, 3-1 and they need to throw a strike. However, it's important for pitchers to be able to throw all pitches from the same arm speed and arm slot, regardless of the count or pitch being delivered.
This is how you throw a fast ball.