I would strongly caution anyone using a pendulum to be sure that you have researched the subject well. As someone else has mentioned, its use is very much like muscle testing. I started muscle testing in early 2006. I was quite ill at the time and unfortunately I didn't read up on it before starting. This was a really bad idea.
There are many things involving pendulums and muscle testing that you should be aware of, such as interference from discarnate entities or spirit attachments. Also, just knowing how to do it correctly will save you a lot of hassle. I went through a lot of hell because I didn't know any better.
You could learn a lot from a dummy (namely me!), so I want to link you guys to a couple threads that I've written so that you can get an idea of what pitfalls to avoid. They are a little long, but I urge you to take the time to read them carefully if you're serious about dowsing or muscle testing. The biggest piece of advice I can give you is to always know what your "yes", "no", and "no answer" signals are before starting. This is really important.
I think that muscle testing is better than using a pendulum because, as someone noted, you will get an answer quicker than if you wait around for the pendulum to start and stop. That is tedious, IMO. Also, if you're using pendulums, you must be certain that it's clean. Most pens are constructed using crystals and they can hold previous energies that you don't want. If you must dowse instead of muscle test, please do yourself a favor and clean it thoroughly by letting it sit in a container of sea salt for a few days. This will neutralize the energies that may have been picked up by the previous handlers, be they from the maker or a salesperson. You can make your own using string and a button, for that matter. This will ensure that you're not getting interference from crystals. Stones and crystals are not a bad thing per se, but they can impart a certain energy that you might not want. Personally, I trust muscle testing way more than pendulums.
Okay, this first thread I made last year at NR before Tom closed the forum. Here you can read the background story of how I started. I ask you to please go to the second thread that I'll link before you try muscle testing, though, as I learned a few more things after I made that first post. The second one is a recent thread that I made at OM, with actual instructions on how to test properly. There is much to be learned from other's mistakes. Please do your homework, and good luck!
http://forum.noblerealms.org/viewtopic.php?id=5594
http://lucianarchy.proboards21.com/i...ay&thread=3750