The server's position in doubles will usually be closer to the center on the deuce side so that she can more easily serve up the middle to the receiver's backhand, forcing the receiver to hit an often difficult, inside-out backhand to keep the ball away from the server's partner. On the ad side, the server will usually take a wider position so that she can either make the receiver hit a stretched backhand or use slice to curve the ball up the middle to the forehand.
The receiver positions herself so that she's roughly on the other end of an imaginary line that runs from the server through the center of the service box.
The server's partner starts in the middle of the service box opposite the receiver. At this depth, she can move forward to an aggressive volleying position to intercept a vulnerable return, but she can also back up enough to hit an overhead on all but an excellent lob. At this width, she can, with one big crossover step, reach across the alley on her side, but she can also threaten the more likely return across the middle of the court.
The receiver's partner stands on or near the service line so that she can move forward to volley if her partner returns aggressively or move back to defend if her partner returns weakly. On the service line, she also has an excellent view of whether the serve is long.
