Spirits and ghosts supposedly control the Ouija board, but I read that it attracts bad energy so its not a good idea to use one.
I grew up with ouija boards. We were never without one. They are pressed particle board, paper, felt, ink and plastic. They don't attract anything but a) the bored, b) the stoned, or c) the gullible desperate. When I was a kid, we fell into category A. When I got older, I fell into category B. I suppose when I'm old and grey, I'll fall into category C.
The planchette moves by light touch. When we used ours, the knees of the operators had to be touching, an awkward position which keeps the body off balance just enough that you won't be able to hold your arms elevated and still for very long. If the surface of the board is kept clean, there will be minimal resistance from the felt on the planchette. The slightest twitch will send it moving. From there it's a matter of the operator's subconscious moving it to form coherent messages.
I noticed, during my lifetime of watching this thing, that the board worked best when one person was somehow fairly submissive to the other, personality-wise. The dominant person essentially controlled the planchette while the submissive person just went along for the ride. When two dominant or two submissive personalites got on the board, it made for "bad conductors", as my family called it. The messages, I noticed, always followed the beliefs of the dominant operator. I believed this to be, as I said, subconscious manipulation rather than any intentional manipulation, based on my personal knowledge of the people at the board.
My family holds reincarnation as one of our beliefs. We would often use the board to learn of past lives. As I got older and more critical of my world, I rooted through our old notes and found so many inconsistencies in the messages as to discount them altogether as whimsical creations of the operators. My belief in reincarnation persists, however based on two things; events and incidents in other areas of my life, and because I find it an interesting and comforting thing. If it was proved one way or the other tomorrow, however, it wouldn't shake my world up.