Start by getting everyone in the group to stand in a circle facing inwards.
Then pick one person and send them out of the room. Whilst they are out of the room, appoint a 'leader'.
This person is the one who (in a minute) will lead the room in various movements (eg stamping feet, spinning, standing on one foot, dancing, singing, etc). Everyone else in the circle must mimic the leader, without giving away who the leader is.
Bring the person back into the room, and commence the game. It's quite funny watching everyone mimic the leader (especially if they pull some crazy manovours :)
The aim of the game is the for person who was sent out of the room to guess who the leader is. They get three chances to guess it right.
The leader then becomes the 'guesser' and the game continues!