From my personal research into the paranormal, it appears that most hauntings and the like are done by malevolent or angry spirits (Sometimes human, sometimes demonic). Human spirits appear to become trapped in the Earthly realm when they were holding onto extremely intense emotions at or approaching the time of their death. This is why hauntings are most pronounced in places where events of tragic suffering and horror occurred, and places where people have committed suicide.
It is thought that energies specifically linked to negative emotions are the ones most commonly associated with trapping spirits, although a sense of 'unfinished business' is sometimes speculated to be on the list as well, resulting in a trapped spirit that is not necessarily angry or malevolent, but desperately seeking some kind of closure.
Another type of haunting is technically not referred to as a haunting but rather a possession (as it refers to geographic areas, not people). In these cases it is a demonic presence inhabiting an area rather than a human spirit. Anyone encountering a demonic presence has justifiable reason to be afraid, or at the very least very concerned. Demonic possessions of both people and places are most commonly (and almost exclusively) the result of occult practices, most often people messing with Ouija boards and other occult paraphernalia or rituals. Ouija is NOT a game.
The most common signs of a demonic presence include the following...
The sudden and inexplicable presence of really BAD odors which vanish just as mysteriously. The most common ones reported include smoke and rotting meat.
Suddenly appearing and inexplicable zones of extreme cold which come and go, usually in a specific part of the house or property. (This may also be related to a human haunting).
Awaking with inexplicable scratches and/or burns. If this occurs and no physical cause can be ascertained, and especially if this occurs in combination with one or more of the other signs, it's time to call in a priest.
A feeling of "heaviness" in the air whenever entering the home. Demons and restless spirits broadcast a negative energy that has a fairly universal emotional effect on those in range. Long term exposure to this energy can lead to irritability and inexplicable boughts of anger or depression.
Objects moving on their own. Demons feed off of energies broadcast by people during negative emotional states. They therefore like to lash out against objects of sentimental significance, such as family photos or heirlooms, religious artifacts, etc. but will sometimes move objects around to instill fear or instigate hostility. This type of activity usually is only reported in the most extreme cases of demonic possession.
There are certain rules when dealing with a demonic presence...
1> Do not challenge it
2> Do not negotiate with it
3> If you can, get out until the site can be sanctified/cleansed.
4> If you can't get out, but have young children, do your best to get them out until the site can be cleansed.
5> Be watchful for changes in behavior in other residents of the home or building. Drastic personality changes are a red flag and the person exhibiting such symptoms should be kept away from the property. If symptoms persist while away from the property, a demonic possession may have occurred.
... The above is mentioned in the event that someone out there may be dealing with a haunting or demonic presence. Many people, when encountering a ghost or what they think is a ghost, make the mistake of thinking it is harmless. In my research into the paranormal, this is RARELY the case. Another thing to note is that demons often emulate humans (often children) to gain the trust of or otherwise trick people.
... So in short, no, I would not be keen on coming face to face with a ghost. If I did though, I'd at least be equipped with some knowledge that might be useful.
- Cham