Students will be keen to contribute stories, and it is worth analysing with them how these stand up to the two key questions. Many turn out to be hearsay: I knew someone who knew someone who saw a ghost.
A newspapermagazine collection of cuttings of "true" ghost stories can be used to develop critical thinking skills, especially on how we can test the accounts. Role reversal can also stimulate thought. Sceptical students can argue the case in favour. Their opponents can be asked to argue against, reversing their own preferred beliefs. The question of how to interpret the "facts", even when they are clear, can develop further into how a student's world view might be challenged by their interpretation of ghosts: if ghosts really are earth-bound spirits, then our world view has to be big enough to embrace belief in an after-life. If they are electro-magnetic disturbances of some sort, physics will provide a complete explanation. More able students may see that natural and supernatural might co-exist. But all should see that "spirits" raise the question, what is the spiritual?