I can dowse with copper rods, usually i can find things and water underground, but I have never tried to do it with a map and pendulum or even with the forked stick.
The good thing with it is that the rods move by themselves and not by any movement that you may do with your hands, whether this is subliminal and you are the thing that knows where the item is and you are transmiting that info to the rods via the slight imperceptible moving of the hands I don't know, but I would think that that is what happens really.
Other than that the rods do move even if you hold your hands rock steady.
A way you can test if it works for you is to get an objext that you know well such as a ring that you wear, and get someone to hide it, take the rods or pendulum and concentrate on the ring, and try to find it. If you can do dowsing then you should find the ring in no time.
"We make choices everyday, some of them good, some of them bad. And - if we are strong enough - we live with the consequences."
— David Gemmell