To start the game, deal out one card (face down) to everyone. Make sure that nobody can see their card when it is dealt out. Each person then takes their card and presses it to their forehead so that everyone else can see it. Make sure though that nobody can see their own card.
The person to the left of the dealer starts off the bidding. For example, that person can say: "1 drink", which means "I'm betting one drink that I don't have the lowest card."
The next person has three options: Drink, See, or Raise. If you don't want to take the chance of being the lowest when the number of drinks gets really high, you can Drink... So if the current level is one you can get out of the bidding by taking one drink.
If the second person does not believe that their card is the lowest, they can raise the level to two (or more ) drinks, or they can say See (say the same number that the person before them did.) The next person has to raise, see, or take two drinks.
Play progresses until every one at the table has stop raising the level. Then everybody puts their cards down, and the person with the lowest card takes however many drinks the bidding was up to. In the case of a tie for lowest, all players with that lowest card have to drink.
Of course, if any players "drank" out of the biding earlier, their cards are not counted and they do not have to drink at the end of the round.