The first player picks a category, such as 'animals' or 'makes of car'.
Once the category has been decided all the players must get into a steady rhythm of 'slap, clap, click, click'. The 'slap' noise is made by slapping your thighs with both hands at the same time, the 'clap' noise is made by clapping your hands together, and the 'click' noise is made by clicking your fingers on both hands at the same time.
Once everyone is doing the 'slap, clap, click, click' rhythm in time the game can begin. Players take it in turns to name something which belongs to the category, but they must say it on the fourth beat of the rhythm (i.e. the second 'click').
If play reaches a player but they fail to say something on the fourth beat then they must drink. If a player repeats something that has already been said or names something that doesn't fit the category they must down their drink. In addition to this, any player who loses rhythm with the rest of the players must drink.