Ghosts

So I have been thinking about ghosts a bit lately and have come up with a dandy of a question. If you find a ghost do you have an obligation to help put it to rest? I mean in most theories ghosts are tortured souls who long for the afterlife. But what if that isn't the case? What if they are actually criminals of some sort. Then how do you know which ghosts should be helped and which ones you should completely ignore? I'm not very helpful today when it comes to answers. Well sometimes the answers are in the questions.