Ouija boards the way we now know them feature a layout of numbers, letters, and the words "yes" and "no" written on them. They come with a planchette, a small, flat device meant to help form messages by pointing at a specific place. Users of ouija boards often report the planchette moving without their conscious effort, spelling out answers to questions or simply answering "yes" or "no." Some believe the answers come from spirits, ghosts or demons. Grave Addictions website writer Beth Santore offers numerous tips for dealing with spirits brought on by the ouija board, such as "Always be respectful when talking to spirits" and "Spirits like flowers and water."

On the Other: There's a Logical Explanation

Skeptics believe they know why the planchette skates around the board: unconscious movement. According to Straight Dope columnist Cecil Adams, answers, when they do come, simply reflect the unconscious wishes of the people involved. A person who is blindfolded and has no idea where the planchette is pointing will often simply receive a string of nonsense letters rather than "spirit messages."

Bottom Line

The ouija board originally was marketed in the 1800s as a parlor game, not as something to take seriously. The planchette on the ouija board may indeed move when one or more persons use the game, However, the reason it is moving is more than likely just the unconscious bodily movement of the people involved and not because of supernatural beings.

Source:

Grave Addiction: Ouija Board Tips

Straight Dope: How Does a Ouija Board Work?