It is very important to understand "Coverage" of the court (with your partner) relative to the position of the ball in your opponents court. See diagram above.
1. If the ball is directly opposite you (not diagonally opposite), you must cover your line. This shot down the line is the easiest (highest percentage) shot for your opponent. Shot A.
2. Your partner will cover the middle. He/she is responsible for Shot B.
3. Shot C is very low percentage and your partner may get to it, but if she/he does not....you both clap and congratulate your opponent on a nice shot.
4. If the ball is opposite both of you in the middle, you both cover the middle. Make them angle the shot toward either line. Much lower percentage. If they hit it hard, the ball could carry out wide. If they dink, one of you can get to it.
5. The game becomes much easier if you just employ the above coverages. Of course, you have to keep the ball in play and/or "place" a winner. Patience and Placement....don't forget the two "P's."