A Seance is a meeting, where individuals meet with a medium. ( A Medium is someone with psychic abilities) The medium is brought in to summon a spirit for you, a spirit you may want to communicate with who is deceased whether it be a loved one, or a friend.
It is said that while performing a Seance the individuals should be in sets of three, no less then three people should try to perform a Seance, you will also need a round or oval table, you need to create a circle, in the center of the table you will need to set food down, something simple, as in bread, this will attract the spirits, light candles, no fewer then three, join hands, dim the lights, then the medium will summon the spirits, and await their response.
When the spirit comes, ask them simple yes and no questions, the spirit may chose to talk through the medium, later on you can ask more detailed questions, if the spirit allows.
Your Medium may be fully awake when communicating with the spirits, some mediums may be in some sort of trance, or half awake when doing this. if you work with a medium who knows they fall into a trance when summoning the spirits you will want to make sure they have an assistant with them to write down what has happened, since they do not remember anything when they wake up.