A very simple way of figuring where to go if the ball is hit with an angle is to flow in the direction of the ball. In other words if the ball is hit left, go left. If it is hit to the right, go right. To demonstrate this in my classes, I divide the court into three parts from doubles line to doubles line. Each part is 12 feet wide since the doubles court is 36 feet wide. If the ball is hit to one of the outer thirds that side becomes the ball third. My players know that they both must flow with the ball so that one must cover that ball third and the other partner must cover the middle third. This correct movement will place you in the middle of their return angle, taking away all the easy shots, leaving them with only the hardest. Now you are making life difficult for your opponents and isn't that fun?