Modern tennis often seems to be an exchange of shots hit from behind the baseline, usually ending with one person hitting a winner or an error. However, the best players tend to use their position on the court to help force an error from their opponent or to hit a winner.
It is much easier to hit a winning shot from closer in. The net becomes less of an obstacle and the court area on your opponent's side is easier to target. In addition, your shots will get to the target (and back to your opponent) sooner because of the reduced distance created by your forward position. The opponent will have much less time to react to your shot and this often results in errors on your opponents side of the court.
The statistics on the ATP and WTA tours show that the percentages of points won increase significantly if a player approaches the net. It is very difficult to win points exclusively from the baseline. Even the best baseline players have a difficult time winning more points than they lose if they are not trying to move forward.
A great thought to encourage this offensive idea is to tell yourself to look for balls that allow you to end up inside the baseline (balls landing on or inside the service line) as the point gets longer. You should also take a step or two in if you feel that you have hit your shot well or gotten your opponent on the run. This will get you moving towards the ball more, rather than moving to where you think the ball will end up. Your opponent will feel a lot of pressure and the point will be more likely to end with their error or your winner.
Brian Coleman is the Senior Editor for New York Tennis Magazine. He may be reached at firstname.lastname@example.org