Baseball is a fun team sport; however, the one drawback is that to play you have to find a lot of people, enough gloves for everyone and a baseball field. For years, kids have sidestepped this problem by playing baseball without gloves and with a tennis ball in place of a baseball. Since the ball does not travel as far, you do not need to play in a regulation baseball field. Pitchers can still throw different types of pitches with a tennis ball.
Locate a tennis ball to use. The newer the ball, the easier it will be to throw a curveball. Tennis balls that are worn down have deep seams and are less likely to break.
Identify the spot on the tennis ball that makes a U-shape. Rotate the ball so that the U-shape appears upside down.
Place your index finger and your middle finger together so that there is no gap between them.
Place the fingers from Step 3 on the right seam of the upside-down U-shape.
Throw the curveball by rotating your wrist forward as you release the ball. Tennis balls are lighter than a normal baseball, so you need a very exaggerated the wrist rotation, harder than you would when throwing a regular baseball.