Here Is what I was taught in regards to working with a pendulum.. "Close you eyes... ask for guidance from the Universe with love and light, working with your Highest Vibration ....
Begin by preparing yourself
Use these words it may help
Then focus and ask for the pendulum to move back and forwards like nodding yes ... and hold it over the chart ... then ask the pendulum to move left to right Side to side like nodding no ... holding it over the chart ...
Hope this helps as another idea to try