The Charleston, explained
Before play begins, everyone passes tiles they don't want. It is called the Charleston, and it is your best chance to shape a hand.
The first Charleston
Every player passes three tiles right, then three across, then three left. Play moves to the right, so "right" is the player who plays after you. Everyone passes at the same time and picks up what arrives.
The second Charleston
Then the players may do it again, in the other order: left, across, right. It is optional: any player can stop it, no reason needed.
Blind passes
On the last pass of each Charleston (the first one's left pass and the second one's right pass), a player who can't spare three tiles may pass on one, two or three of the tiles arriving in that same pass, without looking at them. Everyone still passes three tiles.
The courtesy pass
To finish, partners sitting across from each other may exchange up to three tiles. If they ask for different numbers, the smaller number is used. It happens even when the second Charleston was stopped.
Never pass a joker
Jokers can't be passed in any Charleston pass. Keep them: they make almost any hand faster.
What to pass
Pass the tiles that fit your closest hands least: lone winds, numbers you hold one of, a suit you aren't collecting. Keep pairs and jokers. Tilesday's Charleston lessons let you practice each pass, and in a game the coach can suggest a pass with the reason.
Tilesday plays with its own original card of hands. It is not affiliated with, endorsed by, or sponsored by the National Mah Jongg League or any card publisher.