To play this game you need at least 5+ people but I would recommend 10+ people for a better experience. All sit in a circle with one or more drinks. Each person is given a number like 1 to 10 if you are playing with 10 people.
The person with Number 1 will start by saying their number and then someone else's number e.g. "One Six". The person who is number 6 will then say their number and someone elses ("Six Ten" and so forth. This keeps going till someone makes a mistake or doesn't reply when their number is called.
The forfeits can vary depending on the rules you want to set. Usually it's drink 2 fingers worth.
Hint: A good way to catch someone out when they've had a few, is to keep going:
The quicker you go the harder it is. Eventually one of the 2 people will screw up :)