Pendulums are usually used to obtain YES or NO answers to a particular question. The question must be such that only one or the other answer is possible. That, however, is not the only way to use a pendulum -- it can swing toward the most similar item in the selection and thus show directly the value.
The easiest way to do that is to have a diagram, semi-circular or circular. In the following short video you will see the entire motion, seemingly unsure at first and then stabilizing into a direct line towards the answer.
Practically anybody can use the pendulum, but it helps if you are well connected with your Higher Self. To that end, you can take several Bach flower remedies, such as Cerato, White Chestnut, Sweet Chestnut, Larch and others, in order to enhance the connection to the Higher Self. You can also meditate before dowsing, exclude all external stimuli such as music, voices, ensure against interruptions of any kind and so on. It pays to be alone while dowsing, since it is known that the presence of other people may prevent you from dowsing normally.
To Dowse, You Need a Pendulum
Pendulum can be any weight on a piece of string or rope. Some people take off a ring from their hand and dowse with that; some buy the "usual" cone shaped pendulums made out of brass, while others go for even more specialized forms. Most dowsers like to show off a bit and to have nice (very, very nice) pendulums, which command the attention of all present. It is as if the more valuable the pendulum, the better the results would be!?
Crystal pendulums can be very nice, from those made out of clear quartz to amethyst, rose quartz and what have you. Crystal pendulums will usually have many facetes, while metal pendulums are usually more like cones or tear-shapes.
Some pendulums are hollow so that you may put something in it. It may be water, say with a homeopathic or flower remedy in it, or a witness that directs the energy towards its source. For instance, if you put somebody's hair into the pendulum, then such a combination should, in theory, be sensitive enough to diagnose the vibrations of that person, long distance, that is, even when the person is not physically present.
There are other shapes as well, one of which is the Eqyptian form, which is, they say, used for magical purposes... I personally prefer crystal pendulums, because they add their own frequency to the healing, but "empty" pendulums such as quartz or brass may be better for diagnosing.
Also, you may opt to have one "larger" pendulum to diagnose and clear the space in house, while using the other "smaller" pendulum to work with chakras.