A pendulum is one of the simplest and easiest forms of divination. It's a simple matter of Yes/No questions being asked and answered. Although you can purchase pendulums commercially, ranging from about $15 - $60, it's not hard to make one of your own. Typically, most people use a crystal or stone, but you can use any object that's got a bit of weight to it.
Make Your Own Pendulum: If you decide to make your own pendulum, you'll need a few basic supplies:
A crystal or other stone
Jeweler's wire or string
A lightweight chain
Take the crystal and wrap it in a length of jeweler's wire. When you're done wrapping it, leave a loop at the top. Attach one end of the chain to the loop. You'll want to make sure the chain isn't too long, because you'll probably be using it over a table or other surface. Generally, a chain between 10 - 14" is perfect. Also, be sure you tuck in any poky pieces of wire so you don't jab yourself later.
Using Your Pendulum for Divination
There are several different ways you can use a pendulum for divination - you'd be surprised what you can learn with "yes" and "no" answers. The trick is to learn to ask the right questions. Here are some ways you can take advantage of your pendulum to find out what you'd like to learn. Use with a divination board: some people like to use their pendulum in tandem with a board - the pendulum guides them to the letters on the board that spell out a message. Much like an Ouija board, a pendulum board or chart includes the letters of the alphabet, numbers, and the words Yes, No, and Maybe.
Find lost items: much like a dowsing rod, a pendulum can be used to point in the direction of missing things. Author Cassandra Eason recommends "remote dowsing [in which] you can also scribble a diagram of an area or use a map and hold the pendulum over the map to find where it vibrates to locate water, pipes or even a lost cat that may be hiding in the place identified on the map. Finding the target in actuality is then relatively easy, using your dowsing rods as you walk around the identified area."
If you have a specific but complex question, try laying out a group of Tarot cards with the possible answer. Use the pendulum to lead you to the card that has the right answer. Locating magical sites: if you're outdoors, carry your pendulum with you. Some people believe that ley lines can be located via pendulum use - if you happen to stumble across a location that makes your pendulum go crazy, consider holding ritual there.