You are playing the deuce court and all four players are inside the service line, near the net. The ball comes to you and you are reaching toward your alley to hit it. If you hit it "outside," (down the line) then your partner can cover the middle of the court. Remember that 80% of all balls hit come to the middle. Plus, you will have a chance to make another shot if it comes back. Do not forget your partner has already moved to cover the middle as soon as you moved toward the alley.
So, if you hit the outside ball cross-court you will get your partner killed because he or she has already moved to the middle and left their alley open. Two of the most common mistakes in this scenario are trying to hit the "inside" balls (balls between the two players) to the alleys or outside of the court and trying to hit the outside balls cross court. Remember, when all four players are inside the service line, hit the "inside" balls to the "inside" of your opponents' court (between the two players forcing them to try to hit a low percentage shot to the "outside" of your court) and hit the Outside balls down the line or to the "outside" of your opponents' court.
Inside, Inside - Outside, Outside
Good luck on the courts!