One common misconception when hitting slice is that you want your racquet to travel high to low, or the opposite of the low to high swing path on the groundstrokes.  However, a high to low swing path can result in a chopping motion where the ball lands in the net.

Instead, the racquet path is high to level.  To help develop this technique, stand alongside the net and start the racquet above the net and then slide your racquet along the net, finishing with your racquet in front and on the side of your body.  

This simulation will keep your racquet path controlled and allow your slice to move through the court rather than into the net.

Karl Davies is a tennis professional at the USTA National Campus at Lake Nona in Orlando, Fla.