Three separate forms of divination that are often confused and conflated.

  1. Walking around a mystic circle painted with symbols until the diviner is exhausted to the point of collapse. The diviner then stumbles and falls onto a symbol (or, more simply, a letter) and the reading is done, or another diviner takes the place of the first for an extended reading. This method has a direct linkage to the commonly known Ouija board. Sometimes, the way that the diviner falls (covering one symbol but pointing to two others, for example) is significant.

  2. Wild spinning, sometimes in the form of a dance, until completely dizzy. The dizzy diviner then utters prophecies. The idea is that the mind is "freed" by the state of quite amazing drug-free euphoria produced by the spin. Often practiced unwittingly by children!

  3. Similar to the popular drinking game involving a glass of alcoholic beverage and a baseball bat, the diviner walks or turns in a tight mystic circle complete with symbols and when inevitably dizzy to the point of falling over, the symbol indicated by the diviners prone body is read and interpreted.
It occurred to me when researching this form of divination that the playground roundabout or merry-go-round of which I was so fond as a child could be quite easily turned into a Gyromancy circle! Chalk some symbols, have your friends spin you up, close your eyes, lean out, and drop a water balloon, or your little brother! Come to think of it, the little brother option is probably why they don't have roundabouts any more.

Sources:
The Complete Illustrated Book of Divination Walter Gibson 1973 Doubleday
Various websites.