I just got myself a mission in a form of helping a fellow wizard in trouble. I happened to find my way to Indian bazar the other day and heard a discussion between a boy and the shop assistant about ghosts that keep on disturbing him in his apatment. We ended up hanging out the whole day and speaking about all this stuff (he's a newbie on the field) and I advised him to ask if the ghosts have something to tell him. I don't believe in banishing spirits, if they do such a thing they need to be listened to. Maybe their dead was traumatic and they just want someone to tell about it to before they can accept it and move on etc. Maybe something bothered them during their lifetime and they need to tell about it.. I don't know but it takes a lot of energy and effort to, for example, throw things around when you're not a physical being and if a spirit does that, in my opinion, they want to get noticed and thus have something on their heart.
I advised him to use a pendulum and ask the spirits what are they up to. One of them left when he paid attention to it, but the other two are still there as far as I know.
I'll keep you in touch with this. :)