First you need to be extremely gullible and find a few gullible mates, it really helps if you are all p1ssed, you get a far better result. You all sit around a table with some lettered bits of paper and a glass, the secret is nobody must know who is going to push the glass, that spoils the fun.
It apparently helps if you dim the lights (not sure why) If you have a freaky looking female that can put a scarf around her head and call herself Madam ZazA that would be guaranteed to work.
It can be very dangerous, getting p1ssed enough to believe this crap is never safe!! :-)