It's a wide-ranging subject, and far too detailed to go into explaining everything in the space available here. I'm totally astonished at Jake's report that 'dozens' failed a test. It's reckoned that about 85% or more of people have the ability - it's just that they've never been shown how to do it. And it's not just looking for water, but pretty well anything. e.g., In my army days, one wet weekend, taking 4 inverted waste bins, I had the other guys place an AA battery under one of them at random while I stood outside the room. Using divining rods, I correctly told them which bin it was under time after time. Then I had them try, and to their surprise, they all succeeded too. (Except for one, who declared it witchcraft, and wouldn't take part). But no, it doesn't work all the time. It can sometimes demand a degree of concentration on what you're looking for that isn't available. The state of mind influences the results. If you imagine what you're looking for is in front of you, you'll get an indication it's there. If instead you imagine it's not there, you'll get no result. So the mind has to be open, simply concentrating on what you're looking for. The advice I would give to all non-believers is to be shown how to hold the pendulum or rods, and TRY IT FOR YOURSELF! The chances are, you'll succeed.