Set Up
Players take all the dominoes and spread them out face down on the table. One player shuffles them around on the table and the player to his left starts by choosing a domino. Players continue going in a circle, taking one domino at a time. The amount of dominoes taken depends on the amount of players. If four players are playing, each player takes 15 dominoes. When five or six players are playing, each should take 12 dominoes. Seven and eight players should take 10 dominoes a piece while nine to 10 should take eight. The rest of the dominoes are pushed to the side and serve as the drawing pile or "boneyard."
Playing
The first turn has the player with the double 18 playing it face up in the center of the table. With each new turn, the starting domino will decrease by one. For example, the second turn has the double 17 played. After the double zero has been played, the game is over. If the double domino isn't in anyone's hand, players draw one domino at a time until they find the double domino. The player who plays the double domino can play as many dominoes off of the double as he wishes. The rest of the players can as soon as it is their turn, but only during the first turn.
Players play off the double domino, matching the spots. This is their train. The train should go toward them. If a player cannot play on their train, they draw one domino to match and if it still doesn't match, they place a penny at the end. Players can then play off of their train until the player plays on his train. This removes the penny and closes it to other players. If someone ends their first turn with a double, she must immediately play another domino off of this domino. Players draw one tile if they cannot play on their double and place a penny if they cannot play, leaving the train open for other players.
Each round ends when a player runs out of dominoes or if no players can play. Players then count up the spots on their dominoes to find their score. Points are negative in this game, so players should try to score as few points as possible. Once the last round is over, the player with the lowest points wins.
The Mexican Train
The Mexican train is a separate train that can be played off of by any player. It can be started on the second turn and beyond by any player, as long as they play a domino that matches the starting double. Players place a nickel on it to indicate that it is the Mexican train. Players can play on the Mexican train if they can't play on their own train or any other players. This avoids picking up another domino or opening up your train to other players.