Problem: Often hitting hard serves long.
- For players of average height, hard, flat serves have to just barely clear the net, or they will go long. Only very tall players can get hard, flat serves in consistently enough to make them even begin to pay off, and advanced players rarely hit truly flat serves. Adding some topspin will increase your margin of clearance over the net to several times larger. The most preferred power serve among advanced players has a mix of topspin and slice.
- Meeting the ball too low is like making yourself shorter, thus reducing the vertical angle from your racquet over the net to your target area. A low contact point also disrupts the upward whipping action you create at full extension. You should meet power serves at full upward extension.
- You might be meeting the ball too far back. Generally speaking, meeting the ball more in front of you will make you hit lower. Either you’re tossing too far back, or you’re leaning too far forward before you’ve swung, thus getting ahead of the ball.
from About.com -> Tennis
