Get a deck of cards and two people. The dealer sets a certain number of cards on the table next to each other (the number of cards depends on how drunk you wanna get 4 = easy, 10 = hospital). Then lay another row of cards face down below the face up cards.
The player guesses if the face down card is higher or lower than the face up card above it. If you are right you go to next card and so on until you finish the row. Wrong answers mean you drink the number of swallows of beer equal to the number on the card, the dealer replaces any correctly guessed cards with new cards from the deck and the player starts again from the begining.
The player has to get to the end without missing any. If the face down card turns out to be the same as the face up card above it you drink double.