Sixty-six is a 6-card game played with a deck of 24 cards consisting of the Ace, Ten, King, Queen, Jack and Nine, worth 11, 10, 4, 3, 2 and 0 card-points, respectively.

Dealer is determined by any method acceptable to both players. The deal then alternates between players. Each player is dealt six cards and the top card of the remaining deck is turned face-up to show the trump suit. The remaining stock is placed crosswise on the trump card.

The non-dealer leads to the first trick. A trick is taken by the highest card of the suit led that is in the trick, unless the trick contains a card from the trump suit, in which case it is taken by the highest trump card in the trick. Until the stock is gone, there is no obligation to follow suit or to trump. The trick is taken by the winner, turned face down, and should not be looked at again. The winner scores the value of the two cards in the trick, as shown on the table above. Players must remember how many points they have taken since their scores may not be recorded, and they are not allowed to look back at previous tricks. Once the trick is played, the winner takes the top card of the stock to replenish his hand, then the loser does the same. The winner of the trick leads to the next trick.

The holder of the lowest trump card, the nine, can exchange it for the turned up trump. This can be done only by a player who has the lead and has won at least one trick. This exchange cannot be done in the middle of a trick. It must be done just after the players restock their hands, when no cards are in play.

On his turn when he has the lead, a player may marry a Queen-King couple of the same suit by playing one and simultaneously showing the other. Regular marriages are worth 20 card points and trump marriages are worth 40. A marriage or meld is usually announced in some way to the other player, often by saying the number of points made. The points do not count towards the player's total until he has taken at least one trick.

Once the stock is gone, with the turned up trump taken by the loser of the sixth trick, the rules of play change to become more strict. Players now must follow the suit led (winning the trick when possible), they must trump if they have no cards of the suit led, and marriages can no longer be played.

Closing indicates that the closer has a good enough hand to reach the 66-point target under the stock-depleted rules above. The player must be on lead to the next trick in order to close. It is indicated by turning over the face-up trump card, before or after taking cards to make the hands back up to 6 cards. The rules change to the strict rules given above for play after the stock is depleted. The stock is now "closed" and players do not replenish their hands, and there is no 10-point bonus for taking the last trick. If the closer reaches 66 card-points first, he scores game points as described below. If he fails to reach 66 card-points or his opponent reaches 66 card-points first, his opponent scores 2 game points, or 3 if that opponent has no tricks.

A player who thinks that the points in the tricks he or she has taken together with those from any marriages add up to 66 or more, stops the game and begins counting card points. If the player who stopped the game does not have 66 card and marriage points, then the opponent wins 2 game points, or 3 if that opponent has taken no tricks. If the player does have 66 points, then he or she wins game points as follows.

One game point if the opponent has 33 or more card points.
Two game points if the opponent won at least one trick and has 0–32 card points.