"Seeing isn't believing, believing is seeing"; a quote I think from Peter Pan. Seeing or feeling of ghosts are much the same way. Some people have a natural ability to see ghosts. Some are considered magnets to ghosts. Others the perception of ghosts must be achieved. How?
One needs to be exposed to haunted areas. I'm aware of some people that live in haunted homes. I'm also aware of others who may work in known haunted buildings. I have traveled to cemeteries and haunted places from Chicago to Louisville. My perception mostly centers on my photography aspect. I'm a member of an Investigation Team that involves other people who have various levels of sensitivity to ghosts. They can usually detect whether the spirits are good, mischievous, or bad.
Those that have had no exposure to ghosts may not see any ghosts or images. Yet those that have the perception to see or feel ghosts can detect the ghost.
Presently my photos are kept at: http://hoosierhaunts.myphotoalbum.com/