If you’re right-handed, hook your index finger along the right seam. If you’re left-handed, it should be along the left seam.
Your middle finger should always be kept along the top of the ball in order to get the best leverage. [4] X Research source
Feel free to adjust your own grip as you get more familiar with it. While this is theoretically the best grip, the best grip for you will be one that feels comfortable. Move your fingers around until you find a placement that works for you.
Make sure the ball and your grip on it are hidden until you wind up to throw it. Seeing your grip may tip the batter off and take away the surprise needed for an effective sinker.
As with any pitch, try not to make it obvious where you’re aiming the ball. This can cause you to end up feeding the batter an easy run.
Be careful when throwing the ball like this, as too much rotation in your shoulder or arm can cause injury. If you feel pain anywhere along your throwing arm, take a few days off throwing a sinker.
While you should hold the ball tightly in your hand, do so only with your fingers and thumb. If you press the ball against your palm too much, you risk increasing the friction on the ball and reducing the amount of spin you can get.
As you try and keep your middle finger directly on top of the ball, you should get pronation with the natural rotation of your hand. Make these two moves work together to get the best throw.
