Here’s some etiquette guidelines I am using for a local ladder league. I based them on some from Sun City Festival Pickleball. These are for experienced players. I would add some additional ones for an open recreation league with beginners.
Good sportsmanship is the rule. Yes, we love the game, but it is only a game. Respect all players. Assume the best of each player. Talk to your partner about who takes the middle, about calling the ball, etc. Note there are many different strategies for the middle. Don’t assume anything.
Begin each game by acknowledging the other players, and introducing yourself if you don’t know them. If you do know them, use whatever is appropriate to let them know that you know they are there and are saying “hey.”
If the ball is “out,” and it’s on your side, call it out. If it’s close, give the benefit of the doubt to your opponent. This is hard to do when the game is close but do it anyway. Don’t question the call of the opposing team. If there seems to be a consistent issue, talk to me.
If you step into the kitchen on a volley, or if your partner does, call it. Don’t call kitchen or serving faults on other teams. It’s very hard to judge. If there seems to be a consistent issue, talk to me.
Slams are part of the game. Don’t aim for people’s heads, obviously. If you hit someone, apologize. If you get hit, accept apology and move on. If you don’t like getting slammed (who does?), work on your defense or ask a better player for tips on defending the slam.
Server should announce score and make sure receiver is ready before serving. Work out scoring issues peacefully with other teams if there is a discrepancy.
At the end of each game, find something positive to say to the other team at the net. “Nice game” isn’t always appropriate if in spite of your efforts at sportsmanship you have won 11-0. Find something encouraging to say — at least, “Thanks for playing with us!” is nice. But never leave a game without acknowledging the other team.