When you are at the non-volley zone (NVZ) line, the recommended ready position is different from that in the back court. Keep your paddle up in front of you with the back of it facing the net. Bend your knees and keep your elbows down. Your body should squarely face the opponent with the ball. (The pickle-person on the left should have her legs bent a bit more, but otherwise, she's in roughly the correct position.)
This position allows you to hit balls that come at you hard by "popping" them back over the net. If the shot is very fast, you may not even need to do much except angle your paddle a little open or closed to re-
This backhand ready position is also very useful when your opponent takes advantage of a shot that was returned a little too high—right at his zone for smashing back at you. Backing up probably won't work, because the shot will come too fast for you to get behind it. Instead, stay put. Watch the ball come off your opponent's paddle and gauge where the smash will go. Keep your knees loose, and be ready to move in either direction. Now return the smash--using your backhand.
Why? Because of the way your arm rotates. Besides reaching normally to your backhand side (left for right-handed players), you can keep the back of your paddle facing out and hit above you and on your forehand side. By playing your backhand when you need to hit quickly, you are far more likely to return the smash than if you tried to switch to your forehand.