Playing

Regular pace of the game

East (i.e., the dealer), who received 14 tiles on the deal, starts by discarding one of the tiles in his hand. The discarded tile appears in East’s discard slot on the right side of the game board. For details, see Discarding a tile.
As the tile is discarded, other players have right to claim the tile to complete a set. E.g., if East discards Bamboo 3, and West has two Bamboo 3’s in his hand, West can claim East’s discard in order to compose a Pung. If you want to have the discarded tile, you must indicate your claim by clicking the discarded tile as long as it is visible in East’s discard slot. For details, see Claiming a tile. Players’ claims are evaluated after the Discard delay specified on the Gameplay page of the Preferences dialog box. If you don't want to claim a discarded tile, you can click the game board to accelerate the game.
Normally a tile for a Chow can only be claimed from the player who sits on the left of the claimer (i.e., the previous player in playing order) unless the claimer goes out on the tile (in which case the tile may be claimed from any player). A tile for a Pair can be claimed only if the player goes out on the claimed tile (though some rules might forbid claiming a tile for a pair). For details, see Claiming rules.
If two or more players claim the same tile for different sets, the player claiming the tile for the most valuable set gets the tile. Going out with a discarded tile goes before any other option, and the remaining claims are evaluated in the order Kong, Pung and Chow, first being the most valuable. If two or more players claim a discarded tile for the same set (this is possible if rules allow claiming a Chow from any player, and if jokers are used, two or more players can claim the same tile for a Pung), the player who is first in the playing order gets the tile. The same applies to a situation where two or more players claim the same tile for going out, but you can define otherwise by specifying alternative rules. For details, see Competitive claims for going out.
If a player gets a claimed tile, he must meld the tile set, that is, turn the tiles composing the claimed set face up and place them above the hand tiles. After that, the player who claimed a tile discards one of the remaining tiles in his hand. The next player in turn is the one sitting next (on the right) to the player who claimed the tile.
If none of the players claims a discarded tile, the tile is placed amongst the discards. After that, the next player in turn gets a new tile from the Wall.
The cycle described here is repeated until one of the players succeeds to go out (i.e., to collect four complete sets plus a pair, or an irregular winning hand), or until there are no more tiles left in the Wall, in which case the deal ends in a draw.
After the hand is played and one of the players has succeeded in completing his hand, the points are calculated and paid, and the deal normally passes counter-clockwise to the next player. After each player has been a dealer (and the deal is again passed to the player who started the round), the prevailing wind (or Wind of the Round) changes (in the order East, South, West and North), and the next round starts. The game goes on until each of the four winds has been a prevailing wind.
A complete game of Mah Jong traditionally consists of at least of 4 x 4 deals. Usually there are some extra deals: e.g., if East (dealer) wins, the deal normally does not pass, and in most rules the deal does not pass after a draw (Japanese rules being the foremost exception).

Procedures:
Discarding a tile
Claiming a tile
Claiming rules
Viewing discarded tiles