I found this thread while searching for something else, but I figured I'd weigh in. I have spent the last 9 years learning the art, the do's and dont's. Dowsing is a natural ability, it has nothing to do with the stick, that is just an indicator so you can see the microscopic reaction of your muscles. Think of it like a polygraph machine in the palm of your hand.
One in eight people are natural psychics even of they dont know it, because being psychic is not like psychics on late night television or in Hollywood. All mental images are usually wrong, and mental images steer people- wrongly. Part of what makes a good dowser is what fails others, how you focus on the task at hand. If you are involved your mind is no longer clear, it is why doctors are not allowed to operate on their own family. I'm not saying it cant be done, it can, it is much harder. Say you believe there is gold in a certain hill, you will unconsciously force your dowsing rod. But if your friend asks you to dowse something you have no stake in, you will do much better.
What you search for is as important as how you search for it. Call it setting up the target. Wander through the desert and dowse for water: it can be an aquifer 400 feet below, it wont be helpful, you need to find your nearest, most easily accessible source of water. Same for gold. I'm personally not as good as my kid, I trained him and he is gifted, he can find anything, anywhere. One of the training pieces I made up was hiding $5 bills around the house and making him find it. Watching him work is like watching a master at his craft, he sometimes walks through the bush just following the rods, not even realizing he is on the same path (gps tracked) he was on before. Sadly he is not interested in dowsing, it is not glamorous, but I make him come anyways. But I can teach anyone, if you are close to London, Ontario or near the border, we could set something up. The point of my reply was not to push anything, just to be informative and to help dispel some misinformation.
I think I'm going to write a book on this when I get home from my vacation.