A few friends and/or aquaintences.
The more people you have the more challenging it will be,(more drinking).
Form a loose circle so you can see all of the players. One person will start,(anyone). The object of the game is to count to 20 without messing up. The game starts by the player using their left or right fist and clearly tapping your shoulder in the direction you choose. So if you were starting and you wanted the person to your left to go next, with your right fist bring it to your left sholder and say one. That person has a choice of either continue going to the left or to send it back. You must always remember to count your number aloud. Each player has about a 2-3 sec. grace period if they foul up the game stops and that player takes a drink.
The key numbers you must remember:
1-6: either 1.left fist right shoulder-lft 2.right fist left shoulder-rt
7: On the number 7 who ever in the circle gets that number must put there arms parrallel in the horizontal position which ever the top hand is pointing that player goes next.
8,9: these are the same as 1-6
10: who ever lands on the 10 simply points to who ever they want
11-16: again has the same ruling as 1-6
17: this is the opposite to number 7, which ever direction the bottom hand is pointed is the direction of play.
18-20: is the same as 1-6 as well
Now once you have made it to 20 you may make rules. One of my favorites is changing the numbers eg. 3 becomes 8, and the 8 becomes the 3. Everyone messes up on that one.
The key to the game is to go as fast as you can and try to mess other people up. Its good clean fun.