“Try again: draw a long breath and shut your eyes.” Alice laughed. “There’s no use trying,” she said: “one can’t believe impossible things.” “I daresay you haven’t had much practice,” said the Queen. ~Lewis Carroll Through the Looking Glass
Paranormal stories rely on the author’s ability to create a world which encourages the reader’s suspension of belief. Suspended belief must be applied to all things which can’t be proven but are simultaneously believed in – faeries, superstition, afterlife, vampires, etc.
Sometimes, belief in the supernatural element is not essential to the story. In this case, they are merely there serving as “decoration” it is not necessary for the reader to believe in the element in order to become fully immersed in the story. Other supernatural stories dump the reader right into the “unbelievable” situation, and force them to either suspend their belief or be lost. The most successful techniques take a slower route.
Some of the most successful tales begin with a normal event and introduce the supernatural elements in increasing doses throughout the story. This allows readers who don’t typically believe in these elements, to recognize a plausible reason for supernatural experiences. Readers are more likely to believe supernatural themes which have some type connection to the real world – tabloid stories or folklore.
Having your main character stroll down a real street in a real town and stop for a bagel at a real bakery adds extra reality to your book and helps the reader suspend disbelief once the impossible supernatural elements show up.
~Harper, Steven. Writing the Paranormal Novel
Creating a basis for supernatural occurrences within historical beliefs creates credibility with the reader. There is a reason certain stories survive, and a reason why certain supernatural elements – ghosts, vampires, werewolves – are so widespread. It is because they have a viable explanation and they provide a viable explanation. They are useful to the people who create and perpetuate the stories.
When you’re creating a new supernatural culture, the best place to look for inspiration is a human culture. Fairies might be similar to ancient Celts. Vampires might run their underground society on the medieval feudal model. Werewolves might hold gladiator contests similar to those of ancient Rome. It’s fairly easy to use an existing human culture as a starting point for your nonhuman people. You can research and modify the original culture to suit your purposes.
For further reading check out Steven Harper’s Writing the Paranormal Novel.