Gee I don't see why the skeptic has any thing to be bothered with - dowsing seems to me a pretty harmless activity/pursuit/hobby. If it works, then the dowser is finding what he/she is looking for, if it doesn't work they are having fun wasting time. When someone makes an outrageous sounding claim for dowsing, that person is surely going to attract the ire and attention of the skeptic.
How to successfully dowse:
First lets define what sort of dowsing we are talking about. If it is to dowse for underground water or power lines, I would get a pair of brass brazing rods 1/8 inch diameter and about 18 inches long, and bend them into "L" shape, so the short part goes in your hands. Then walk around the area to be searched in some kind of pattern, not in a wandering way, while holding the pair of rods in your hands out in front of you but with elbows bent and not held tightly - the rods must be able to move easily. The rods should be almost level with the ground but just slightly downward, so they stay pointing ahead. As you walk, the rods should start to point in the direction of where water or power lines are buried; then as you pass over the water/wires the rods should cross. If you then stand on the spot where the rods crossed, they should react by pointing away from each other, showing the general direction of the water vein or wires.
Wind can spoil your efforts completely by moving the rods so you need a calm day. I have read of many other possible problems from watches, clocks, the moon etc but in my very limited experience only the danged wind gives me fits.
If the dowsing is to be for buried treasures or a mine etc then I don't have any suggestions, since I have never tried this. Map dowsing is also something I
don't have a
bit of experience with. However just looking for water or power lines I have had good luck.
I did
not believe it worked until I
saw it and tried it, but still have not found a good way to differentiate between electric wires or water, nor how MUCH water is 'down there'. The depth methods I have tried seem to work, but not that accurate, at least not within a foot or so. Of course I am very much a neophyte to dowsing, NO expert and don't claim to be able to detect buried treasures or dowse maps - can't even tell between water or electric wires for that matter!

Anyway for someone wanting to
try it, it is very inexpensive for the 'equipment' and lots of fun!
Oroblanco