The Curveball is generally a more advanced pitch to learn and throw because of the unique mechanics involved. Many coaches feel that younger players (below the age of 15) should not practice throwing the Curveball with real baseballs because it might place too much stress on a young arm. Although it is likely much safer to throw curveballs with a Blitzball because of its light weight, younger players should still ask parents' for their approval before trying to learn it (you might want to learn a hard Knuckleball instead to get a similar dropping action without having to throw actual Curveballs). The Curveball is unusual because it is the only pitch that involves "topspin" (think of it as the opposite of a fastball's backspin).
Master the "two-seam" fastball. Once you effectively use the two-seam grip and arm motion, creating sinking action on the ball, you will be better prepared to throw sliders. For the two-seam fastball, place your index finger and your middle finger directly on the narrow seams of the ball -- the top of the "U" in the stitching. Put your thumb on the bottom of the ball, on the smooth surface of the ball directly under the fingers. Grip the ball tightly to create friction and movement. Use the same arm motion as on a regular or "four-seam" fastball.
Gripping a curveball is simple. Place your thumb on the bottom seam of the baseball and then place your middle finger directly above your thumb; splitting the baseball in half with thumb and middle finger. Your index finger is placed right next to your middle finger. Make sure your index finger applies no pressure on the ball. When you start throwing the curveball you can experiment how tight you want to grip the ball. If your grip is too tight the ball can “squirt” on you or it will not make it across the plate. If your grip it too loose you will lose complete control and the ball won’t even know where it will go. Thumb and middle fingers are the only two fingers that apply pressure on the baseball.
Ok, so I know this whole page has the best baseball pitching drills on it, but out of this whole page, these are my two most favorite drills. The first is the wall drill and the second is the rocker drill. The second drill in this video is the same as Stevie’s favorite pitching drill that you’ll see below, but I go into a little further detail on how to perform this pitching drill correctly in this video. Check it out!