Grip the ball with your pointer finger and middle finger on the outsides of the seams, running along the seams. To make this clearer, grip it along the seams, then slide your two fingers out to the outside. Have yoru thumb and ring finger under the ball, about the same spot under the ball as your two fingers are on top. This provides support and accuracy.
When you throw, snap your wrist to give the pitch more "pop" and it will drop better. The best affect will come if you throw this pitch overhand rather than 3/4 or sidearmed. Pitch it low in the zone. Leaving it high may lead to HR's.