Play with two or more packs shuffled together. This is ideal if you're playing with five or more people. It'll make the game last longer and it will be harder to tell who is actually bluffing.[4]
Change the sequence of ranks. Instead of playing the cards in ascending order of rank, play in descending order of rank. Start with twos, and then move back to aces, then kings, then queens, and so on. You can also play by going with the next highest or the next lowest rank of the person who went before you. So, if that person puts down a nine, you can put down a ten or an eight.[5]
You can also allow the next player to put down the same card as the player before him or her, or the card below or above that card in rank. This will make it easier for each player to actually put down a card he or she has.
Allow players to put down more cards than they said they had. This rule should be decided before the game starts to avoid any accusations of cheating. If this rule is in effect, a player can say he's putting down three cards, for example, while sneaking in a fourth card. You can still call "bullshit" on this player to check if he actually put down the correct amount of cards; if he lied, then he'll have to take the pile
Allow players to put cards down when it is not their turns, but not the most recent player. Follow all of the same rules, but anyone can go at any time if the player who should go takes too long.
5
Allow people with all four cards of the same rank to discard them off to the side, when its their turn, face up, telling everyone what rank it is. This helps make a shorter game. If you have for say, 3 nines, try to call BS when someone puts down the nine, hopefully it has a nine, then you can discard the nines. This is great especially if the pile has 3 cards, excluding the nine. Then, the number of cards in you hand goes down. Once the rank is put discarded, skip it next time. So if you or someone else discarded nines, it will go 7,8,10,etc, as long as those ranks are still in the game.