There are many variant rules, but the most popular way of playing is presented here. The goal is to win exactly the number of tricks bid, neither more nor less.
Each game comprises a series of deals. In the first deal, each player receives one card; in the second deal, two cards; and so on to the limit. With four players, there are 13 deals; with five players, 10 deals; with three players it is advisable to limit the game to 15 deals.
Having completed the deal, the dealer turns up the next card of the pack. The turn-up fixes the trump suit for that deal. When the last deal leaves no odd card to turn up, the deal is played at no-trump.
Beginning with the player to the left of the dealer (the first hand), each player in turn bids exactly the number of tricks that they expect to win. Thus, on the first deal the possible bids are "One" and "Zero." The total of all bids need not be equal to the number of tricks in play. After the dealer has bid last, it is a responsibility of the scorekeeper to announce "Over," or "Under," or "Even," according to how the total of bids compares with the number of tricks.
The first hand makes the opening lead. Each player must follow suit if possible. If a player cannot follow suit, they may trump or discard at will. A trick is won by the highest card of the suit led or, if it contains trumps, by the highest trump. The winner of a trick leads next. A player is entitled to be informed at any time how much any other player has bid, and how many tricks each player has won. Each player should keep their tricks arranged in an orderly fashion so that they may be easily counted.
How to Keep Score
A scorekeeper must be appointed to record the bids and enter the results. A running account is kept of each player's cumulative score.
A player who takes more or less tricks than their bid scores nothing for the hand and loses nothing (though in many games, one point is scored for each trick taken). For making their bid exactly, a player scores 10 points plus the amount of the bid. (As yet there is no standard for scoring of "Zero" bids. In different localities the score is 10, 5, or 5 plus the number of tricks in the deal.)
The player with the highest cumulative score at the end of the game wins, and the winner gets a bonus of 10 points. Each player settles with every other player on the difference in their final scores.