I personally think Ouija boards only work because you're unconsciously moving the pointer it's called the ideomotor effect. http://en.wikipedia.org/wiki/Ideomotor_phenomenon

http://www.youtube.com/watch?v=rMtuWymUzz4

I think for a psychic who uses the ouija in their profession to prove it's not the ideomotor they should blindfold themselves while using it to see if what they write makes any sense.