Mahjong manners as translated by me from the JPML site. Japanese link at the bottom of the article. Enjoy!
– When you sit at a table, say hello.
It’s polite to greet your fellow players when you sit at a table to play mahjong. Doing so will leave a good impression on them. [Translator’s note: Do people need to be told that?!!!]
– When the tiles come up [on an automatic table], push your wall forward at a slant so the right side is closer to the center.
This makes it easier for people to take. If the left side is forward, a player may not see a tile and take the wrong one.
– When building the wall, make sure you place the last tile down (in the king’s tiles or dead wall).
A tsumo from a tile drawn after declaring a kan (rinshanpai), equals one more fan. Thus it is a very important tile. If it is accidentally knocked over and prematurely shown, it could create an unfair advantage.
– Do not moupai (feel the tiles).
Wait until the player before you has discarded their tile. Taking a tile and waiting for the player before you to discard could result in an illegal action. You are not leaving any time after the previous player’s play for pon, chi, kan or ron before starting your own turn. Being able to feel the tiles is good, but I have seen people get it wrong and discard their winning tile after reaching.
– Treat the tiles with respect.
Be careful to not knock tiles from the wall or drop them from the table. If you hit the tiles against the table, you will make other players feel uncomfortable or intimidated. If you’re not careful, you may even damage the table [in the case of automatic tables].
– Line the discard piles in lines of six.
Long lines of discards are difficult to see. When someone has reached, it’s difficult to work out when that happened if you have long lines. They also restrict the discard space of the player after you.
– Play as quickly as possible.
Get in the habit of placing the tile you just drew in your hand AFTER making your discard. You should get into the rhythm of deciding your potential discards while other players are drawing to ensure that play is smooth.
– Play mahjong with only one hand.
It may not be possible while you are still getting used to mahjong, but try to always play with one hand.
– Make clear and distinct calls.
Everyone on the table should be able to hear your calls. If your call is indistinct or too quiet, others might not be able to hear it.
– Don’t give anything away about your own hand during play.
Mahjong as a game becomes pointless if you reveal information about your hand. Psychological word games are not part of mahjong. Therefore, do not say anything that could lead other players to speculate about your hand.
– Don’t tut.
You shouldn’t tut when paying other players or when someone tsumos. It makes other people feel uncomfortable. Of course, you should also refrain from humming, whistling, singing, tapping, crossing your legs, wearing hats or sunglasses etc.
– Don’t display your tiles with one hand (when you win).
Using only one hand to put your tiles down a few at a time looks clumsy. When displaying your tiles or pushing the wall forward, use both hands.
– Be polite when paying with sticks.
Do not throw or drop sticks when paying. Instead politely place them near the person you are paying. It is good manners to place them on the table so that everyone can see them and not pass them into someone’s hand.
Original Japanese article: http://www.ma-jan.or.jp/jan-up/class_1/04.php