Exorcism as far as Bardon's system of Hermetics is simple in theory-
Find out the source of the entity, find out what its affinity is with regards to elements, then fill the room or the person with the element it doesn't like, which weakens it (if it doesn't force it out altogether), then you just command it to leave.
Of course, in practice it's a little bit more complicated, because it requires you to actually be able to perceive the source of the entity. If it is truly a self generated entity then there's nothing an exorcist can do. Even if they "destroy" it, the root problem will remain and it will only be a matter of time before it rears its ugly head again.
If it truly is an external entity (self sustaining energy form, possibly with its own level of intelligence, does not require someone to generate it), then it requires the exorcist to be able to correctly perceive its attributes. If it's an entity with a fire affinity, then fill the room with water energy. Of course, it's not like it's going to TELL you how to get rid of it, it's going to do its best to try and trick and deceive you, so it all comes down to the exorcist's level of correct perception.
As far as safety is concerned, knowledge is the best tool. If you know the source, then you can know what it's going to try and do, so you can be prepared. If you have it cornered, it's going to try to attack. Not necessarily because it wants to hurt something, but because of its instinct for self preservation- it knows its cornered, and it knows you can kill it or forcefully send it away. So prepare accordingly. And by this someone from Bardon's system would say just have great willpower.
Taoist exorcism methods, I would imagine, would be similar, using various methods to focus either 1) the will, or 2) the proper elements to get rid of something.
Edited by Sloppy Zhang, 31 January 2010 - 09:26 AM.