Believe it or not, there's more than one way to haunt a house (or plantation or inn or military academy). Learn about different types of hauntings here.
A garden variety "haunting" is a repeated manifestation of strange and inexplicable sensory phenomena at a certain location--a.k.a spooky stuff in the crib. But does this always mean that we're talking about an actual ghost? Nope, it doesn't--at least not all the time (but we'll get to that later).
For now, let's talk about ghosts. Hauntings occur with no regularity and for no particular reason. Some weird stuff may manifest on occasion or even continually for a few days or hundreds of years; others may only occur on certain anniversaries; and others may be totally random.
It is generally assumed that hauntings involve apparitions, or ghosts, of the deceased. In fact, apparitions are seldom seen. Most hauntings involve noises like footsteps, a tapping or knocking sound, strange smells, sensations like the cold prickling of the skin, cold breezes, and the feeling of being touched by an invisible hand. Other hauntings involve poltergeist-like activity such as solid objects being moved, broken glass, doors that open and close by themselves, and manipulation of lights and electrical devices.
People who visit haunted locations also report a variety of emotions, including anger and fear. Many cases like this are mistakenly called "evil" or "demonic." Other places seem to involve friendly, or at least harmless, emotions. In these instances, there is no need to call the Ghostbusters out of retirement.