Pendulums have been used for over hundreds of years for various uses: spirit contact, asking Yes/No questions, locating items, etc. They are one of my favorite tools for my studies, and I feel everyone should have one. So here is some information about this fascinating item.
WHAT ARE PENDULUMS
Pendulums are typically some sort of crystal or gemstone on the end of a chain. You can find them in precious gem or rock stores, or online. The type of stone it is does not matter. You can even make your own. Pendulums are a form of dowsing, or 'water witching'. Dowsing is an ancient practice used to find water, gems, or other objects.
CALIBRATING YOUR PENDULUM
Once you have acquired a pendulum, its time to calibrate it. To do this, hold your pendulum by the end of the chain, and ask it an definite 'yes' question (e.g. is the sky blue). Be sure to keep your pendulum very still. The pendulum will begin to swing in some form: up or down, clockwise or counter-clockwise. This is its way of showing 'Yes'. The stronger it swings, the more definite the answer is. Do this for 'no' as well. Once you have calibrated your pendulum and are aware of its Yes/No motions, you may begin asking it questions.
Besides asking questions, pendulums can be used for a variety of different things. Finding lost objects is another common one; to do this, simply ask the pendulum where the object is and the direction it swings is where it is. Or you can perform a sort of '20 Questions' to find an object. If you had lost something in your house, you can go around into the different rooms and ask the pendulum if it in this room. Once you find the room the object is in, ask the direction it is.
Spirit contact is another use for pendulums. I have not yet experimented with this yet and I encourage you to look more into this. A basic for of spirit contact using a pendulum is having it over a spirit symbol or board (similar to a talking board) and begin asking questions.