(from "Bridge for Dummies")
Most bridge players value a reliable, happy partner above anything else. It's important to the success of your partnership that you work together as a team. You both want to win, so you can't gain anything from getting upset when play doesn't go exactly as planned. It seldom does! Here are a few tips on keeping your partner one happy camper.
Treat your partner like your best friend
Even if you don't know your partner well, treating her with respect improves her play. Treat your partner like your best friend, and you'll be repaid in "spades." Be a pleasant, courteous opponent, and you'll win everyone's "hearts."
Tolerate your partner's errors
Don't keep harping on your partner's errors just forgive and try to forget (at least until after the game). After all, do you want to be reminded of all the mistakes you've made? (Everybody makes mistakes, including you.) If you have constructive criticism, save it for after the session, when you'll both be calmer. Expect (demand) that your partner show you the same respect.
Keep a poker face
Never make any facial or body mannerisms that indicate whether you're pleased or displeased with a bid or play. You'll lose the table's respect. Facial and body mannerisms can be construed as illegal signals.
Deal well with disaster
A truly good partnership handles the inevitable disaster with a touch of humor. If your partner doesn't have to worry that you'll have an apoplectic fit whenever something goes wrong, he'll play better.
Play conventions you both want to play
Don't force your partner to play your favorite conventions. A partner worried about a convention inevitably makes more errors in the bidding, play, and defense, not to mention screwing up the convention if it comes up.
Pick up the slack for the weaker player
The better player in a partnership should make the weaker player feel at ease. Make your bids, leads, and signals as simple and clear as possible, and don't give an inexperienced partner tough contracts to play. When you judge that it's going to be a tough hand to play, bid conservatively.
Own up to your own errors
Avoid the human tendency to lay your own errors at your partner's doorstep. It makes a weaker partner feel good to know that you, the stronger player, make errors as well and are a big enough person to admit them.
Offer words of encouragement
Give your partner a few words of support after the hand is over, particularly if he doesn't make his contract. "Tough luck" and "Nice try" go over better than "My great-grandmother could've made that hand in her sleep."
Treat your partner the same whether you win or lose
When the session is over, win or lose, tell your partner how much you enjoyed playing with her (no matter how you feel). Kind words mean the world to a player who knows that she hasn't played well. It also shows class.
Know when to have fun
When all is said and done, you play bridge to have fun, and so does your partner. You've done your job if your partner leaves the table happy.
Other partner etiquette issues:
What is the Etiquette When You Double Book?
What happens when you accidentally “double-book” (i.e., make two dates) and both partners show up expecting to play with you? Since you made the mistake, the proper etiquette is to first offer that your “dates” play with each other. If one of them declines, for whatever reason, you must ask one of them to bow out (with apologies for your blunder, of course). Making a replacement date as quickly as possible is also appropriate.
Finally, it is unethical to look at your partner's face to gauge their reaction to your bid or play.