Not my cup of tea, but student's manuscript of necromancy believe, and how to work with spirits. Thought me that Yerba mate is good component to stop untruthful spirits(and by the way, all spirits must be taken us such, at first).
And punishment of necromancy in our Christian religion has been, stoning, as we have it in the Bible.
Book says that best to work with are these that has been soldiers, policeman or fireman, as common with service of duty work, Intellectual ones doesn't have enough energy to work well as they use it for philosophical experiences in afterlife, and drunk spirits are not good eider as they are unproductive and can drag you to alcoholism.
Also the necromancer is responsible for actions of the spirits,working with these that stayed on Earth, by own wish or else. So its quite reasonable being.