They're real they do work most often the spirits whom are contacted through the ouija are those whom reside on 'the lower astral plane,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.
Consider cleansing yourself spiritually before using the board, Meditate and try envisioning yourself surrounded by a bright light, Take an herbal or salt bath.