Gameplay

The entire deck is dealt one card at a time facedown to the players. It is generally considered more important to have every card in play than for each player to start with exactly the same number.

The center of the table will hold a pile of cards played during the game. Play starts with whoever has the two of clubs (or ace of clubs in some versions of the game) in their hand and continues clockwise.

On each turn, the player must play the cards he has of a certain rank. There are two common variants of the game. In the first, the rank must be one above the rank played by the previous player (twos, then threes, then fours). In the other, it may be one above, one below or the same rank as the preceding player. The player selects the cards to play, announces how many are being played and their rank ("two fours"), and places them facedown in the pile in the centre. If the player doesn't actually have the cards needed to play at least one of the correct rank, he is still required to play, and so must cheat or bluff (lie about it), hence the names of the game. It is also permissible to bluff if the player does have cards of the given rank, for example, by playing and announcing "two Kings" when he has only one.

The next part of the game is subject to two major variations. After each player takes his turn and before the next player has, one of two things can happen. In the first variant, any of the other players can yell out "Cheat" or "Bullshit" to challenge the cards that were just played. In the second variant, only the player about to lay down cards can yell out "Cheat" or "Bullshit" to challenge the cards laid down instead. In some games, the players agree to either wait before playing their turn so other players can think carefully about challenging, or to rapidly take their turns to put more pressure on challengers. When a player yells out to challenge, they turn over enough cards from the top of the pile to decide if the cards just played were legitimate (this should be the number of the cards that the player who just took his turn announced; however, it is generally acceptable to turn over more if cheating as described later is suspected). If it turns out that the player played the amount and rank of cards that he announced, the challenger takes the whole pile that had accumulated in the centre. If the player was bluffing and did not put down what he announced, he takes the whole pile.

Depending on how you want to play, either the first player to get rid of all his cards (and not lose any challenge on his final play) is the winner, or the game may continue to determine second place, third, etc. Since Bullshit is almost never played for money or other stakes, players who don't have cards because they've already won may decide to a challenge that they intend to lose so they can get cards to continue playing.

Other methods of cheating

While bluffing is a necessary rule of the game, there are additional ways to cheat. Some players find these unacceptable, while others consider them to be part of the game. Probably the most common technique is to play more cards than you announce, but keep legitimate cards of the number you announce at the top of the stack. If you are challenged and the challenger turns over only the number you announced, this cheat will not be detected. This cheat can be compensated for by turning over more cards than the number announced, but this may have the undesired side effect of revealing whether the previous player was lying about his cards, even though his turn passed unchallenged. He would not be required to pick up the pile at that point, but this revelation could give away information about the contents of his hand or about his playing strategy.

Another method of cheating is to hide cards from your hand so you don't have to play them. Other techniques can be adopted from those of poker collusion and mechanics of poker cheating.

Strategy

When playing with the most limited number of cheating options, strategy is relatively simple, making the game trivial and mostly chance for adults. Calculate ahead which cards you will need for the next few rounds so you can maximize your legitimate plays and bluff away the cards you won't be able to use legitimately.

Strategy becomes more complicated as more cheating options become available:

For all rules:

• Generally, if you find yourself almost certain to be called on your turn, consider taking the risk and calling someone before you so that the penalty incurred is less. Sometimes, the penalty will be so small players will decide not to call you out.
• If you have exactly the cards you need to win without ever having to lie, generally it is best to not to call bullshit on anyone unless they will for sure win before you.
• If you have a very large hand, you can sabotage other players by switching legitimate cards that you do have with a variety of cards. For example, you have 4 aces and it's your turn to call aces. However, instead of putting 4 aces down, put down a King, a Queen, a jack, and a ten. When another player gets bullshit called on them, they will find themselves with 3 additional sets of cards to get rid of.
• Sometimes it's best to let a losing player slide in order to increase the penalty on the winning player.
• Act. As in poker, sometimes having a good poker face or intentionally having a bad one can minimize the number of times you are called.

When lying about the number played is allowed:

• When the game starts, know what your next cards must be. Determine what the last card you would have to play to win on is (requires quick thinking). Only applies to incremental rules
• When playing your turn, if there is already a stack, try to throw in an additional card or two so that the last card you must play to win on is shortened.
• When playing your cards, play them as a neat stack, as this makes it more difficult to determine the true number.
• If you have a large hand, use that opportunity to remove even more cards, as most players won't call unless you've constantly BSed.

Russian Bullshit

Some people find this variant, also known as Chinese Bullshit or (ambiguously) as Cheat, to be more interesting than the regular variant. The strategy for two-player Russian Bullshit is particularly intriguing.

Deal out all the cards to all players, as evenly as possible. The first player to go chooses any rank to start with, and places any number of cards of that rank face-down. For example, the player may play "three Kings" or "five fours" or "eight jacks". Bluffing is, of course, permitted.

The next player chooses from these options:

1. Play more cards of the same rank, not the next higher rank as in regular Bullshit. The player may add any number of cards.
2. Say "I Doubt It" (i.e., "Bullshit"). Note that you may only say "I doubt it" if it is your turn. If you are right, the previous person picks up all the cards and you start a new round. If you are wrong, you pick up all the cards and the next person starts a new round with the rank of his choice.
3. Say "I Believe". If you are wrong, you pick up all the cards and the next person starts a new round with the rank of his choice. If you are right, all the cards on the table are removed from the game and you start a new round with the rank of your choice. This option is not used in some variants.
4. Pass. This option is not used in some variants; it allows more skill in bluffing because nobody is ever forced to lie. If every player passes, the cards on the table are removed from the game, and the last player to play a card starts the next round.

Although you cannot challenge if it is not your turn, you are usually allowed to verbally advise the person whose turn it is to challenge.

The bluffing encouraged by this game becomes apparent when, for example, there are 16 supposed "queens" on the table from two decks of cards. Some rounds of play will escalate to the point that there are ludicrous numbers of cards in play, but nobody wants to challenge, because of the risk of picking up all the cards if the previous player was telling the truth.

After one player goes out, the game may continue to determine second place, third, etc.