Etiquette
American Mahjong has its own set of table manners, mostly unwritten. Here's what to know before you join a group for the first time.
At the table
Don't touch another player's tiles or rack, even to help. If you're not sure whether a hand is complete or a call is valid, ask instead of reaching in.
Keep the game moving at a reasonable pace once you're comfortable with the basics — long pauses on every turn can slow the whole table down. It's completely fine to take your time while you're still learning — most groups expect that.
Try to hold your tiles and rack so others can't see them. It's part of the game, not a trust issue.
If you're new
Say so at the start. Most players are glad to slow down, explain a call, or double-check your hand before you go out. Nobody expects a first-timer to know all of this by heart.
Bring your own card if you have one, but it's fine to share with your neighbor if you don't yet.
General courtesy
Show up on time — a missing fourth player holds up the whole table. If you have to cancel, give as much notice as you can.
Keep side conversations light during play so everyone can hear calls and discards. Keeping your phone on silent is standard at most tables.
If you're playing at someone's home or a club, it's common to bring a small snack or contribute to the table in some way — ask your host or fellow players what's typical for that group.