For my own lousy memory I want to get down the rules of Liar's Dice as taught to us by Ryan. There are plenty of variations of this game (well covered by the Wikipedia article) but these are the Riley house rules and it's how we roll*.
5 six-sided dice (D6) for each player
Some sort of cup to conceal each player's dice (if you can get pewter goblets, you rule)
All players shake their dice in their cup and then upend it so that the dice rest on the table and are concealed from everyone. Each player peeks under their cup to determine the values of the dice.
Someone** starts the bid. A bid is assertion of the total number of a certain value of die present on the entire table, taking into account that 1s are wild. For example, a bid of "five 4s" is an assertion that there are at least five of some combination of 4s and 1s present under everyone's cups.
Play proceeds clockwise. The next player has the choice of raising the previous bud or challenging it as inaccurate.
Raising a bid requires increasing at least one of the two values (number of dice and value of dice) and decreasing neither. For example, a bid of "five 4s" could be raised by a bid of "six 4s" or "five 6s" or "seven 6s" but could not be raised to "four 5s".
1s are a special case -- in value, 1s are 'higher' than 6s, and once the bid has reached some number of 1s, future bids can only increase in number, not value of dice. But when jumping to a bid of some number of 1s, the number can decrease, but not below a minimum determined by this formula:
(the current bid number divided by two) + 1
and then rounded down
Whew. So... if the current bid is "seven 6s" the minimum bid of 1s would be (7/2)+1 = 4.5 which is then rounded down to 4.
If you think the previous bid is incorrect, you challenge by saying "Liar" or "that's a lie" or "j'accuse" or such. All players then reveal their dice and push the relevant values (the bid value and 1s) towards the center to make counting easier.
If the bidder was correct, the challenger loses a die. If bidder was incorrect, they lose a die. Whichever person lost a die starts the bidding on the next round.
When a player loses a die and then only has one die left, the next round is their Mustache Round. Each player only gets one Mustache Round per game.
The Mustache Round is announced by everyone with a call of "Mustache Round!". After each player throws their dice, they hold a finger horizontally under their nose to pantomime a mustache. This is very important.
(Maybe not, but there are actual gameplay changes in a Mustache Round:) In a Mustache Round, the one-die player goes first and the dice value that they bid cannot be changed in subsequent bids and 1s are not wild. For example, an initial bid of "two 3s" could only be increased to "three 3s", "four 3s", etc.
When a player loses all of their dice, they are out of the game (though they may still place a finger under their nose for Mustache Rounds). Play proceeds until only one player still has dice and they are the winner.
* Pun intended.
** Roll for it, earlier, or youngest starts or "not it" or something. Not really important.