Dowsing is using some form of "divining rod" to search for a substance or mineral. In U.S. history dowsing was used primarily to find water. Today I have seen it used in a variety of situations from identifying the width of someone's energy field to choosing a lot to bid on at a coming auction.
Of course, as with most psychometric applications, there are those who stolidly refuse to believe it works.
Remote Viewing is a type of "free response" psi. That means that you don't know the question, and the answer could be anything.
Dowsing is a type of "forced choice" psi. That means you may or may not know the question, but the answer could only be one of a limited number of things.
Dowsing in my experience can be done a nearly infinite number of ways -- creativity matters -- but there are 5 main approaches to it:
1. Rods. Historically, dowsing was used to find water and minerals underground, and a tree branch was held in the hands of an individual who would pace an area, and when they were over the element searched for, the rod would seem to bend in their hands of its own volition. (It's considered this is a subconscious muscle issue, and that the water or mineral may be picked up through some unknown, subtle physiological path.)
In the modern day, as well as one rod held in two hands, you can also use two rods in two hands. When this is done, the rods are very simple -- a close hanger bent into an "L" shape, with a stiff plastic tube (something between a straw and pvc tubing) on the short side. You hold the short side, with the long side either at top or bottom (doesn't matter, but usually it's done at top), and settle yourself until they are straight. Then you can ask them to swing to point to something, or you can walk with them and ask them to swing (open, closed, or some direction) based on a variety of info. From practical stuff like measuring where the water lines are, to more esoteric stuff like measuring the energy-field around someone's body, rods are pretty useful once you get the hang of them. Again, the assumption here is that subconsciously we know the info (whether through psi or the body or both) and that subconsciously our muscles are causing the movement.
(My point is: the dowsing rod/rods are not like a ouiji board. Nothing's moving on its own. Generally. ;D)
2. Pendulums. This is some kind of weight, preferably somewhat pointed, hung on a string or chain. Brace your elbow against a table, and lean your hand out a bit; hold out the pendulum till it is above the table in string-length. Like the rods, "how" this gives info can vary depending on how you are using it. You can hold it still and then ask for a rotation to tell you yes/no (or little/no/sluggish rotation for 'other'). You can start it moving just a tad but then ask (it will happily change direction ). You can instead use a chart, like a piece of paper with different answers or concepts on it, and either hold over the middle and see what it swings towards (a bit tricky since it swings two ways obviously...) or move around so you're above each area and see which one if any cause motion.
3. Kinesiology. You can use muscle-testing on yourself or others, although in my experience this is more amazing on others for some reason and doesn't have as much second-guessing yourself. Muscle testing is a technique that is pretty cool for a variety of things, from finding out whether a food or vitamin is good for you -- and how much of it -- to asking questions that require psi to be answered. It is also used as a form of 'communication from the subconscious' although of course, all forms of psi are considered to be that. I used to have a chiropractor who used kinesiology in his work and he was awesome. You can find more info about this on the net. It's really something everybody should try with others at least once in their life, it is pretty amazing when you realize it works. This is considered 'subconscious', not psi. Generally. If you are asking for information that could only be known via psi (a word used to basically sum up "some kind of info transfer we really don't know what to call, but it isn't anything physical we know of, so we call it psi") or attempting to ask questions of the nature devas and trusting they will cause your body to provide the answer, then we could get iffy on those details. This is good for yes/no, and when working with yourself, the "finger strength" test is the one most commonly used. Sometimes this works for me and sometimes I can totally fake it out, so I reserve judgement I guess.
4. Map dowsing, timelines, or other formats where there is a paper or "representative" object that you physically put your hands (or ruler, or pencil, or something) over and attempt to "feel" the "area" that corresponds. For example the dowser might hope to feel a warmth, cold, tingle, sharpness, resistance, or something--anything--over some part of the 'representation' that would give a clue to where something is. Sometimes this is done with a ruler, from several directions, a line drawn at each point, and then it's triangulated basically for an 'area'.
5. Mental dowsing or other mental-structural-tools. For example, you can visualize a stoplight, where red means no and green yes, and then imagine total darkness, and then ask your mind to show you real fast the answer -- and whatever you see first flash, take that as your answer. There are many creative tools you can construct with imagination and these can get pretty complex -- if you practice constantly this is doable but otherwise the visualized structures don't tend to be very coherent or consistent. (This is similar to some shamanic and magick work.) Again, unless you are looking for data that requires psi to obtain, this may as well be considered a subconscious technique, akin to "going with your first impression" on a multiple-choice SCANTRON test. ;-)