Beginners Curve
The beginners curveball is just "that". A great pitch for young begining pitchers. Basically this pitch does the exact opposite as a fastball. Where a fastball spins from the bottom to top known as "backspin", a curveball spins from top to bottom. Also instead of leverage coming from behind the top of the baseball as in four-seam fastball, leverage on a curve comes from the front of the baseball. Here's how it works: Grip a baseball leaving the index finger off, like you were pointing at something. Your index finger will be used to aim the baseball at your target. Next, place your middle finger along the bottom seam of the baseball and place your thumb on the back seam (as shown in the middle picture below). When this pitch is thrown your thumb should rotate upward and your middle finger should snap downward while your index finger points in the direction of your target. This is the reason this pitch is great for beginners. The ball goes where your index finger points. The beginners curveball helps to align your hand and ball to the target and gives a beginner great movement on the baseball.
Knuckle Curve
Another more advanced variation of the curveball is the knuckle curveball or also known as a spike curve. Thrown the same way as my beginners curveball only you'll tuck your finger back into the seam of the ball. Your knuckle will now point to your target instead of your index finger like in the beginners curve. This pitch can be difficult at times. Many pitchers who are learning this pitch for the first time aren't comfortable with the "tucking" part. But when mastered most pitchers feel this grip gives them the most rotation and most movement of any breaking pitch. It's not super comfortable at first to tuck your index finger into the baseball so it doesn't get a lot of use by less skilled pitchers.
Overhand Curve
The straight curveball or "overhand curveball" is one of the most common breaking ball grips. It's a variation of both beginners curveball and the knuckle curveball. A straight curve requires mastery of my beginners curveball first then once the basic principles are mastered from both grips. This doesn't mean that you have to throw a beginners curve, just master the grip. Most pitchers actually start right out with this pitching grip. But the beginners curveball is a better place to start. Then move up to this pitching grip. For that reason there is no significant difference between a straight curveball and a beginners curveball except for the finger placement of your index finger (compare below photo to beginners curveball). Your index finger should be placed on the baseball as opposed to pointed at a target. The thumb action of the pitch is upward. The thumb rotates up while your middle and index fingers rotate down. The arm action on this pitch is a little abbreviated at the end. Instead of getting a nice long arc of deceleration and finishing throwing elbow outside of your opposite knee as with your fastball, you'll want to bring your throwing-hand elbow to the opposite hip. This shortens your follow through, but allows you to really snap off the pitch giving it a huge curve making it that much harder to hit.
