Equipment
To play 42, players will need a double-six set of dominoes and a cribbage board to keep score. If no cribbage board is available, players can substitute a pen and paper.
The Deal
After the dominoes are shuffled, each player will draw seven domino tiles that will make up their hand. There is no boneyard or draw pile in a game of 42. Once the players have their tiles, the bidding proceeds.
Bidding
The player that is holding the 0-1 tile bids first. Bids will be in number form, ranging from 30 to 42. The players each will have a turn to bid or pass, and bidding must increase the previous player's bid. Once the bid reaches 42, bids may only be raised by doubling the bid.
Gameplay
Suits in dominoes follow the number displayed on the tile. Each tile follows two suits. For example, a tile with a three on one end and a five on the other end can follow either a three suit or a five suit. The highest bidder names the trump suit and lays a tile in trump suit to begin the game. All players must follow suit, unless they have no matching tiles, in which case they can play any tile. If a trick leads with a trump suit, players must play a trump. However, if a trick is led with a non-trump suit then they must follow suit on the higher end of the tile.
Scoring
Each trick is worth one point. If the bidding team meets the amount they bid, both team will score their points. If the bidding team doesn't meet their bid amount, they receive a score of zero and the other team scores their points. A game is played until one team reaches 250 points.