Hi Yrreg,
I once took part in a ouija board session. A cup obligingly slid around on the table, spelling out words. It claimed to be a spirit and showed a strong interest in one of us; by an not-very-astonishing non-coincidence it was the one with the biggest ego in the room and the only one of us who explicitly believed in the paranormal. It told him lots of flattering things about how special he was. He was apparently related to Merlin. It showed a marked interest in Arthurian and Celtic myth, just like Mr Big Ego. However, when challenged to provide specific and verifiable data (such as the day of the week on a given date or a checkable historical event) it completely failed to do so.
All that was happening was that my egotist friend was (consciously or unconsciously) guiding the cup and making it say things that he wanted to hear. No magic, no spirit, just an attention seeking young man playing parlour games.
Ouija boards do work, at least in the sense that they will spell out words, but there is no magic or spirit involved. The phenomenon is a result of
ideomotor action, little unconscious movements of (in this case) the hands, triggered by thoughts alone, with no conscious direction or intent. These ideomotor movements are always happening.
In the case of ouija boards, those taking part are primed to expect the cup/glass/planchette to move around and spell out words, so this is the direction in which the unconscious movements guide the planchette. It is simply much more interesting for it to work than it is for it to do nothing, so when a tiny movement pushes the planchette one way, it triggers another ideomotor movement that increases the movement or guides it in the direction that seems most likely to form a word. These movements add up and, before you know it, the planchette is flying around the board at an impressive speed.
It is the same trick that make table turning work.
If you doubt this explanation, try doing the ouija board whilst blindfolded. The results will be gibberish.
Here are a couple of links which I urge you to take a look at;
Ouija board - The Skeptic's Dictionary
Ideomotor phenomenon - Wikipedia
I would also recommend the stage magician Derren Brown's book "Tricks of the Mind", where he goes into the truth behind such practices as ouija boards and spiritualism, especially the practice of "cold reading". Brown is quite capable of putting on an impressive show of "psychic" ability, including ouija boards, but it is all just stage magic. That's all it ever is.
Mutate and Survive