No Man’s Land
You may have noticed that when the opponent hits a ball to your feet, it is usually impossible to return it well. You may not have noticed that the easiest place to hit to one’s feet is in in the mid-court, the area between the non-volley line and the baseline. When you’re just inches behind the non-volley line, your opponent cannot usually drive a ball low to your feet. When you’re at the baseline, they can only hit the ball so hard without risking it going out, and you have time to move forward and scoop it up. But there in the middle, you’re in what’s often called “no man’s land,” “dead man’s land,” or the “kill zone.” Or, to be politically correct, perhaps it should be called “no person’s land.”
So what do you do? Make sure you are always at the baseline or at the non-volley line. In most cases, if you are on the serving side, stay put until after the ball is returned, then run forward to the non-volley line and stay there for the rest of the rally, unless an opponent lobs the ball. If you are on the side receiving the serve, you can move to the non-volley line as soon as you have returned the serve.
There are exceptions. For instance, you want to move forward with your partner. If one player is staying back, and the other has moved forward, the opponent has a nice wide diagonal area between the partners into which to drive the ball.
If in the middle of play, you find yourself in that middle ground, move to the non-volley line as quickly as you can.
Many players tend to stand a foot or so behind the non-volley line. That is not as strong as being an inch behind the non-volley line because that little extra distance gives the opponent more opportunity to shoot for your feet, and you less opportunity to shoot for your opponent’s feet.