As already pointed out, rule one of Mao is: "The only rule I can tell you is this one." If you read the other rules, are taught them by anyone, or learn them in any way other than actually playing the game, you're a dirty cheater.

Unfortunately, the first rule makes it particularly easy for an experienced player to cheat. Since a new player is ignorant of the other rules, he has no way to tell if somebody starts making stuff up just to screw him. Are you finally starting to get the hang of the game? Are you, against all odds, about to actually beat somebody? You may discover that Aces and 7s suddenly switch functions for no reason, and you'll be given cards for drawing out of sequence. Take another card for "misaligned seating," and five more for "failure to recite the digits of pi backward while dancing the funky chicken." Oh look, you're losing again, how about that.

When this happens, Mao stops being a card game and turns into a lame joke. The newbie can't possibly win; the instructor might as well be cheating at solitaire. This is particularly pointless since an ignorant newbie has a very small chance of winning even a fair game of Mao.

Worse yet, the victim of this pathetic and stupid scam is now scarred for life. He'll find it almost impossible to figure out the real rules, now that this random garbage has polluted his internal cache. He'll probably lose many, many more games, even against people who play fair, as he tries to reconcile the garbage with the actual rules. This is not fun, and will likely make him give up on the game altogether.

I've seen it happen, folks, and it ain't pretty.

If this has never happened to you, you should stop reading now, lest you spoil the fun. But for the poor unfortunate victims, keep going to find out the real and actual rules of the game.

Mao works a lot like Uno or Crazy Eights. On each player's turn, he places a card from his hand on the discard pile, in such a way that it matches either the suit or the rank of the card already on top of the pile. If you cannot legally play a card, you must instead draw one. The winner is whoever runs out of cards first. This is the easy part.

It gets slightly interesting when you add the modifier cards:

  • A 2 reverses the order of play.
  • An Ace skips one player.
  • A Jack is a wild card. As soon as it hits the pile, anyone may call out a suit, and the first suit called is now the suit in play. If two people speak at exactly the same time, the first one to repeat himself wins.
  • Any spade requires the player to state the name of the card. In the case of the Jack, he must say "Jack of Spades" before he can call a suit.
  • A 7 forces the next player to draw one penalty card before his turn. Whoever played the 7 must say "have a nice day." For each additional 7 played in succession after the first, the speaker must add the word 'very', and the penalty draw is increased by one. (E.g., if I play the fourth 7 in a row, I say "have a very very very nice day," and the person after me draws 4 penalty cards.)

The real killers, though, are the rules of conduct:

  • After doing something wrong (a "violation"), the guilty player must draw a card.
  • Cheating is of course not permitted. Note that breaking a standard rule is always referred to as "cheating," even if done accidentally (which is usually the case).
  • No one may touch his cards before the dealer picks up his hand.
  • No talking is allowed, unless required by another rule, or while in a Point of Order (see below).
  • No swearing is allowed.
  • Asking about the rules is not permitted.
  • Lying, including bluffing, is not permitted.
  • The active player must play a card within 5 seconds of the start of his turn.
  • A player who has one card left must say "Last card." Failing to do so is a double violation: one for lying and one for cheating.
  • Upon playing his last card, a player must say "Mao." Failing to do so is a triple violation: one for lying, one for cheating, and one for "failure to honor the name of our great leader" (or simply "failure to win").
  • Saying "Mao" any time when you didn't actually win is a violation. This is "taking the great name of Mao in vain," on top of whatever else you did (lying, cheating, probably playing out of turn, etc.).
  • If you catch someone breaking a rule, you must hand them their penalty card and explain what rule was broken. For this purpose only, you are exempt from any rules against speaking or touching cards.
  • "Point of Order": As soon as those words are said, even unintentionally or in a sentence, all players must put their hands face-down and not touch them. Talking is allowed, and the time limit rule is suspended, but players still may not discuss the rules of the game. Saying "Point of Order" again before the point of order is ended is a violation.
  • A point of order ends when any player says "End Point Of Order." (In some variants, only the player who started the point of order can end it.) Players pick up their cards and continue the game. The "no talking" rule comes back into effect.
  • The "add a new rule" rule is a regional variant. If it is in use, the winner of any hand makes up a new rule based on cards played and/or phrases spoken, which remains in play for the rest of the session. New rules may not remove or completely contradict old rules, though they may overlap. As with the rest of the game, the new rules are discovered only by seeing what happens when they're broken.
There are tons of other variants, like the jokers wild rule in tiefling's writeup, but they vary based on where you play the game and from whom you learned it. AFAICT, the rules I've listed are common to most groups.