The first Charleston
After the deal, every player chooses three tiles to pass. Everyone passes three tiles face down to the player on their right, picks up the three received from the left, and looks at them. Then three tiles are passed across, then three to the left. This first Charleston is compulsory.
Tiles received can be passed on in a later step, so a tile you do not want need not stay in your hand.
The second Charleston
After the first Charleston, any player may stop the second. If no one objects, players pass three tiles to the left, then across, then to the right. The direction reverses because it mirrors the first Charleston.
Some players love the second Charleston as a chance to improve; others stop it when their hand is already strong.
Blind passing and the courtesy pass
On the last pass of the first Charleston (left) and of the second (right), a player who does not want to break up their hand may "steal" by passing on some or all of the tiles just received without looking at them — a blind pass. Finally, players opposite each other may agree an optional courtesy pass of up to three tiles; the smaller number offered is exchanged.
Jokers may never be passed, at any stage.
Charleston strategy
Pass tiles that no hand on the card you are considering can use, and watch what comes to you — repeated passes of the same suit hint at what others are not collecting. Avoid passing pairs that could form pungs with jokers, and beware of passing tiles that a neighbour clearly needs. The Charleston is the first real decision of an American game.