You have probably heard this before. If you have, sorry to bother you. Most divination of this sort; ouija, pendulums, table tipping, etc., is caused by the subconscious of the people participating.
The Palanche (that thing that you use with a ouija board, or in your case, a glass) can move without any knowledge or direct intention of the participants. The expecations of the sitters increase or decrease this potential. For example: you were all waiting for the glass to spell out your fiancee's grandma's maiden name.
She might have unconsiously begun to move the glass in the proper direction. Then you and your other guest unconsciously helped her by pushing the glass the way that she wanted. The whole effect snowballs upon itself as everyone involved is being positivly rewarded for their unknown actions. As your mind practices more (spelling out more and more words), it gets better at the action. Eventually the palanche is flying across the board like it was possessed. (This is described as "Autosuggestion" on another page. - ed.)
Try this experiment with a pendulum to test the underlying principal. Give someone a pendulum (anything will do) and have them dangle it comfortably over a table. Take two coins and place them on either side of the pendulum and ask your subject to imagine it moving between them. Say something like "the coins are like walls that the pendulum cannot pass through." Through variations of this you can get the pendulum to swing up/down, left/right, in circles, and so on.
Now tell your subject that their subconscious will answer questions for them, the code will be: swinging left/right = yes, that up/down = no and circles = I don't know. Ask them questions.
It should work. it will probably work better if they don't know that you are testing this on them. Expectations raise the possiblity for success.
I am not trying to say that your original experiment is invalid, but instead, giving you a new direction of exploration. What does "subconscious" mean? Why or how does it know these things that we may not know consciously? I don't know, I just exploit these rather unknown truths in my performance.
I have to get back to work. I am actually writing a seance for theatrical purposes.
If you have time, let me know how the experiment goes.
Oh, you may reprint this, but please leave out my name. Magician's oath and all.
skeptika's note:
If anyone else conducts this experiment and wants to pass on the results please email me at skeptika@yahoo.com
As for myself, I have seen this sort of thing done by my beloved for the purposes of divining the number and gender of children a woman is going to have. She dangles a ring from a hair and holds it over the stomache of the woman being 'divined', if you can call it that! If the ring goes back and forth, that is a boy. Circles is a girl. The ring stops and starts again with each child. I don't think she's done it since she tried it on a girl in her early 20s who was very keen to have children and the ring refused to move at all, signifying that she would have no children. Hopefully the ring was wrong.