Now first thing is first! You must learn the geological, physical, and spiritual differences between ghosts and how to effectivly deal with them.
Depending on what culture the ghost previously lived one will greatly determine what the cure is for it. This can be accomplished through research, speaking to them, or for more hostile ones--binding them (using a talismen, charm,incantation, etc.) Using bindings can be difficult if you can not tell how powerful the apperition is. As for physical, treat it as a clue to how they got there. Example: Headless, perhaps had head chopped off or seperated from head post burial...goal likely to find missing head. Also it determines what type your up against. Example: Shadow child, do not touch...very skittish and possibly acts as poltergeist...dangerous must be binded by incantation because charms and talismens pass right through it.