From Shar Roach Hkodesh – Yichudim

-Sometimes the Nefesh (lower soul) of an evil person is not yet able to enter purgatory, this is due to his many sins.
-This spirit must wander around. Sometimes this spirit will enter the body of a living person and poses him.
-Rabbi Chaim Vital brings down a Yichud to remove the sprit from the body. He writes that he himself tried it out.
-The person performing the exorcism must be in a state of complete holiness and purity, he must immerse in a mikva before the process.
-The possessing spirit dresses itself in the pulse, the pumping blood of a person.
-One takes the hand of the possessed person, feeling his pulse.
-The exorcist then meditates, focusing on the spirit. He then starts saying the verses brought down in the Yichud, permeating the Divine Names coming out of them. He meditates on the names coming out from the number of words and their beginning and end.
-The possessing spirit will then begin to speak from inside the body, the person performing the exorcism can then ask it questions.
-Sometimes in order to get the spirit to speak, a shofar must be blown next to the ear of the posesed body. One also has to meditate on the name KRA SATAN, with SHVA vowels on all the letters.
-The sprit will be very reluctant to speak, so as not to be embarrassed from the people in the room.
-When the spirit does speak, the body of the host stands as still as a rock. The voice of the sprit leaves the mouth with out any movement from the lips.
-The voice will sound very thin like the voice of a child.
-When the spirit raises itself through the body so it can reach the throat to speak, a small round lump will be seen rising through the skin of the neck. The same moving lump can be seen when the spirit move down to exit from the toenail.
-The spirit will often lie when answering questions about its name and identity. He will lie and give the names of other people and much misleading information. Sometimes he does this to make mockery of the person doing the exorcism, other times he does this so he cannot be decreed to leave the body.
-One must threaten the spirit with excommunication and bind him with the power of divine names, that he will not lie and he will say only the truth.
-Know, that the possessing spirit does not come alone, rather he comes with a devil of destruction that watches over him and punishes him for his sins.
-This is what Dovid meant when he cursed the wicked people “Appoint upon him an evil one, and a devil shall stand on his right side.”
-When the spirit receives permission to rest in a human body it is not a constant state, it must leave the body at certain times to receive additional punishment. During this time, the devil that was appointed over him, enters the person to guard the place. The person cannot be cured until they are both removed.
-When one meditates on the Yichud he must try to remove the spirit from the body. If he does not leave then the verse must be repeated and the names must be meditated on again. After each round the exorcist must yell with strength “Leave, Leave Now”
-The main thing is dependent on the exorcist ability to strengthen himself like a worrier, and to not be afraid of the spirit at all.
-The sprit must be bound and decreed that it will not leave the body from any place other then in between the foot and the toenail, of the large toe. When the spirit leaves the body it can cause a lot of physical damage, when it leaves from the toenail the damage is minimal.
-One must also bind the sprit with an oath of the Holy Names that it will never hurt or posses another member of Yisroel again.