There is, as there should be, some etiquette to the game. If observed and practiced, it will both speed up the game and make it more enjoyable for all.
1. When a ball is served to you and it is out, do NOT hit it back. Either let it go, or hit it into the net. When you hit the ball back or run to retrieve the ball on a serve that is out, it is disruptive to the server and slows down the game.
2. If your opponent(s) call your ball out, ACCEPT the call - they can see it better than you.
3. The server, when beginning to serve, should CALL OUT THE SCORE in games, and during serving, call out the points in that game. The scores should be called out loud and clear so that everyone on court can hear it.
4. Do NOT call a double bounce on the other side of the court. That is up to the player that made the infraction. If you stop play because you thought there was a double bounce, and that player disagrees with you, then you lose the point - remember, it's their call.
5. To avoid injury, when retrieving a ball and returning it back to the serving court, do NOT hit it back at random. Call out the receiver's name and "ball coming" before returning the ball, so that the player is aware.
6. Also to avoid injury, when passing by another court, please walk quickly and stay as close to the fence as possible. Do NOT run across another court when play is in progress, unless they have waved you through.
Of course, all players should know the RULES OF TENNIS. However, there are two rules of tennis that a lot of players don't seem to know:
1. It is an infraction to touch the net at any time - the USTA says "The player may not touch the net, or the opponent’s court with anything he wears or carries or with any part of the body". If you do, you lose the point.
2. You cannot hit a ball on the other side of the net - the USTA says "A player may break the plane of the net on a follow through from a shot as long as the ball was on that player's side of the court when the ball was struck." (This means your racquet may cross the line of the net - as long as it does not touch the net, and as long as the ball was struck on YOUR side of the net.) Again, if you do, you lose the point.