This is the basic fastball that just about every pitcher throws.
Grip the ball with your top two fingers across the seams and with your index finger and middle finger across the seams at the ball's widest point. But don't grip it tightly – grip it like an egg in your fingertips.The key is to get the ball to leave your hand without much friction.
Put your thumb under the ball across the bottom seam. Your index finger and middle finger should be about a half-inch apart. Too close together, and you're throwing a weak slider. Too far apart and it will cost you speed. If you move your fingers slightly off-center, the ball should break a bit.
There should be a little bit of a gap between the palm of your hand and the ball. When you release the ball, let your finger tips roll off the laces.