This one is real simple. Now you have to make sure of one thing. DON'T TELL ANYONE.
That's rule number one, and the only rule.
The game is rather simple. You get a bunch of people together and sit down. Tell everyone the name of the game and thats it. Also make sure to find out who knows how to play.
Start by asking the person to your left "One Up, One Down / Two Up / Or Two Down" and they gotta answer with one of those. Usually its judged by how your arms are positioned. Is one arm up and one down, both up under your chin or both down. Now if their wrong, they gotta drink. If their right, they are done.
Keep going around the circle asking each person in turn the same question. You can make it difficult by changing positions but don't make it too obvious or they catch on.
Thats pretty much it. Feel free to add/change your own rules. Its a mean game, but its fun watching people attempt to learn.