Indeed there are many anecdotal tales of very weird events and paranormal phenomena taking place during and sometime immediately following Ouija sessions. And this has led to the warnings that the Ouija is not a game at all, but a dangerous tool.
Ghost researcher Dale Kaczmarek, of the Ghost Research Society, in his article, Ouija: Not a Game, says: "The board itself is not dangerous, but the form of communication that you are attempting often is. Most often the spirits whom are contacted through the Ouija are those whom reside on 'the lower astral plane.' These spirits are often very confused and may have died a violent or sudden death; murder, suicide, etc. Therefore, many violent, negative and potentially dangerous conditions are present to those using the board. Often times several spirits will attempt to come through at the same time but the real danger lies when you ask for physical proof of their existence! You might say, 'Well, if you're really a spirit, then put out this light or move that object!' What you have just done is simple, you have 'opened a doorway' and allowed them to enter into the physical world and future problems can and often do arise."
The Moving Glass Séance/Ouija Page offers some other suggestions for how the Ouija operates:
Autosuggestion - Autosuggestion is where the participants unconsciously control the movement of the glass or pointer. Something, possibly the combination of the random and minor spasming of the muscles of the participants, drives the glass in a random direction. This random movement would, one would expect, lead to a random distribution of letters which would, for the most part, appear as gibberish. However, despite all good intentions, there is likely to be some editing by the participants. The participants begin to subconsciously guess ahead and the letters come out in a generally orderly fashion.
Self-delusion - Self delusion is where the belief of the participants drives them to subconsciously control the movement of the glass or pointer. A sort of not quite intended fraud. This is very like autosuggestion except that one or more of the participants actually controls the movement of the glass, albeit subconsciously. They hear the question, they know what needs to be spelt out and their fingers subconsciously push or pull the glass in the direction of the required letter.
Telekinesis - If telekinesis (or psychokinetic ability) exists, there is a possibility that in a séance the questions are answered by those who ask them. The participant who knows the answer also controls the movement of the glass or pointer. It is likely that control of the movement is subconscious, so the mechanism is closer to self-delusion than to fraud.
Telepathy - If telepathy exists, it is again a possibility that in a séance, the questions are answered by those who ask them. The answers are broadcast and the whole group then subconsciously knows the answer and they all ensure that the correct answer is achieved.
Some take the use of the Ouija so seriously that they suggest certain rituals be performed before a session to "cleanse" the board. Ouija Tips for a Smooth Session suggests lighting white candles and to be extra careful when using the board on bad weather days. At Using a Ouija Board, Linda Johnson, who believes the Ouija is a form of channeling, warns, "Do not choose a place where you suspect earthbound entities are gathered: graveyards, haunted houses, sites of tragedy. Choose a place that feels good - has the right vibrations, a home where loving people live, or a room usually devoted to learning and meditation. Start with a meditation where you concentrate on cleansing your own body, aura and chakras with a visualization of silver rain; filling your bodies with white light; and call upon your guides to protect you and ask them to allow only information and entities through for your highest good."
Ouija, Using It Without Harm says, "The Ouija can be a useful tool for mediumship (spirit contact), but can also be a tool to tap into the subconscious minds of the users. It is believed that we know more than we realize and often the answers are inside of us. In this way, it can be used to develop your own psychic powers without having to dig up some spirit of a questionable nature. The Ouija is what each person or group makes it."