The Big Little Book of Magick

Next, you must establish the Yes movement of your
pendulum. Hold the pendulum in the proper position
and ask it to show you a Yes movement. It will do this
by either swinging sharply forward and backward or in a
clockwise circle. After it has shown you the Yes
movement, again ask it to stop.

Yes Movements

Now you need to establish a No movement. When
asked to show this, the pendulum will move either in a
sharp side-to-side motion or a counterclockwise circle.
After it has established the No movement, ask it to stop.

No Movements