American mahjong has official rules. It also has a whole second rulebook that never makes it into print.
Break those unwritten rules and nobody will disqualify you. You just might find that the good Thursday table is suddenly "full."
Here's what experienced players expect.
Sighs, gasps, groans, a little happy wiggle when you draw a joker: they all give information away. A great table is a calm table. Save the celebrating for when you call Mahjong.
Place your discard clearly in the center, face up, and say what it is: "Four Crak." This isn't just good manners. It's the rule, and it keeps everyone on the same page.
Wait until the previous discard has had its moment before you pick up your next tile. Grabbing too early steals another player's chance to claim it, and it's one of the most common sources of table friction.
If you want a discard, say "call" or "Mahjong" clearly. Don't lunge. And never touch another player's rack or tiles, including her exposures, unless you're making a legal joker exchange on your turn.
Coaching someone else mid-hand ("Oh, you should go for the 369!") is a big no, unless you're at a teaching table and everyone has agreed to play with open hands. Unsolicited advice gives the whole table information.
Pass promptly, pass the right number of tiles, and don't take forever deciding. If you want to stop the second Charleston, say so clearly. And remember: jokers are never passed.
This one needs saying out loud more than ever. A player who's texting or scrolling slows the game, misses discards, and signals that the table isn't worth her full attention. Phones face down or off the table during play. Check between hands. If something truly urgent comes up, excuse yourself and step away.
When the winning tile lands, call it promptly and clearly. Hesitating lets play move on and complicates the whole round. Just double-check before you expose your hand. A false Mahjong with exposed tiles makes your hand dead.
Take the time you need on a tough decision, but don't make three people wait on every routine discard. If you're a beginner and still finding your rhythm, just say so. Most tables are wonderfully patient when they know.
If you're a guest, ask how the table plays before the first deal. If you're the host, share your house rules up front. A two-minute conversation prevents a whole afternoon of friction.
At the end of play, everyone helps gather and count the tiles and pack up the set. It's a shared responsibility, not the host's job.
These norms exist because mahjong is, at its heart, a social game. The tiles are the mechanism. The people are the point.
Be the player everyone hopes gets seated at their table.