Today I had a workshop in a beautiful church. A huge building with endless empty wooden benches and colourful windows. The chanting of a men choir reverberated constantly from the walls. Creepy setting. Just what we needed for our ghostly session.
Last week we went on a "ghost walk" around our old English city (more of a town, but as they 'lately' built a cathedral, it can name itself city now). A tiny, gaunt old lady told us various stories surrounding quite a few buildings in Leicester city centre. Some of my classmates even believed to have seen the hooded hunchback that supposedly follows passengers when they walk home from the famous market through a long alley. His distinct footsteps shall be audible from behind all the way down. Similarly freaky was the monk that comes around the cathedral corner and points at the person in a group that won't have to make any plans for birthdays anymore.
A good ghost story, according to Noel Carroll, uses a variation of "onset" (first manifestations of the unnatural), "discovery" (learning about the unnatural), "confirmation" (convincing of the unnatural) and "confrontation" (approaching the unnatural). These seem to be very useful starting points.
More crucial, I would say, and it is partly hidden in his suggestions, is the need to evade clichés and deal with the hesitation between the natural and the supernatural, because a reader will naturally struggle to belief. This way one can build up the uncanny, a term in the German language describing both the scary and the homely. A contradiction that has more in common than you might think.
How do you make the supernatural believable? Is it about setting, character or voice?
I believe setting would play as part of the biggest believability factor here. How can the reader get into the 'mood' of ghostly adventures in a bright, cheerful daycare center? But if there is a whistling wind accompanied with a baby's wail, and there are NO babies here--and the crack in the ceiling drips when there is no rain, in the puddle, you can see the baby's reflection.
Also, I think voice adds to it. Characterization, well, how can we believe in the surroundings when the character laughs and is so happy?
Ghost tours are cool. I don't write horror, but there are unusual aspects about the characters in my books, and I've grounded their unique abilities with science. (Not technical details, just implied.) Not sure if that helps you or not...