Warm-up serves . Take all your warm-up serves before the first serve of the match. Courtesy dictates that you not practice your service return when your opponent practices his serve. Player makes calls on his side of the net . A player calls all shots landing on, or aimed at, his side of the net.
Opponent gets benefit of doubt .
When a match is played without officials, the players are responsible for making decisions, particularly for line calls. There is a subtle difference between player decisions and those of an on-court official. An official impartially resolves a problem involving a call, whereas a player is guided by the unwritten law that any doubt must be resolved in favor of his opponent. A player in attempting to be scrupulously honest on line calls frequently will find himself keeping a ball in play that might have been out or that he discovers too late was out. Even so, the game is much better played this way.