“The only rule I can tell you is this one” Is a phrase commonly used among all variations of Mao. As the point of Mao is for players to learn the rules by observation, generally, the above phrase is the only rule that veteran players may share with new ones.
That is to say, the only rule you can tell a newbie is “The first rule is that I cannot tell you the rest of the rules.” Explaining the rules of Mao would defeat the purpose of the game.