A pendulum should be small and relatively lightweight. A crystal bead is ideal. It should be just heavy enough to swing freely from its cord. The pendulum cord can be made of thin string, embroidery silk, fishing line or even a slender jewelry chain, as long as it is light enough to swing freely, strong enough not to break easily, and flexible enough not to kink or readily form knots. The cord should be approximately ten inches long. If you want it longer or shorter, you will know after a few rounds of questions. Some New Age and occult shops sell ready-made pendulums which are fine if they have not been used before.
Always cleanse and consecrate your pendulum when you get it (or make it) before its first use. Keep it on your altar, preferably wrapped in some favorite little cloth or pouch. You may want to carry it around with you in your pocket or purse. Try to keep it wrapped to keep out distracting vibrations, and do not let anyone else use it. Others may ask it questions, but you are always the one who holds it.
To use it, hold the pendulum cord lightly between thumb and forefinger. Ask your question in a form which is suitably answered with a "yes" or "no." The query may be aloud or silent. Do not move your hand. The pendulum will move by itself (that is the whole idea.) Experiment for a while to determine how it works for you. A helpful technique is to ask the pendulum "What is your movement for a 'yes'?; next, ask it "What is your movement for a 'no'?. This should be repeated several times until you are sure of your pendulum's response. The movements will appear to be combined if the matter is not yet decided, or if the answer is literally "yes and no" or just plain, stupid.
How does it work? Some say there is a special spirit of the pendulum. Another theory is that the user plugs into the Collective Unconscious, where all knowledge and answers reside. Another: we each tap out own inner wisdom when we concentrate on the pendulum's swing.