One person is blindfolded and is the Blind Cow. The Blind Cow is led to the centre of the circle and spun around, they then wait for the game to begin. A bell should then be passed around the circle and rung as it is passed. The Blind Cow will then follow the sound of the bell. The game leader then points to the player with the bell who should stop ringing the bell. The Blind Cow now has to guess who is holding the bell (by pointing). If the Blind Cow is right, the two swap places. Otherwise the game continues until the Blind Cow guesses correctly.
Source: From the original site.