Read books of accomplished horror authors, such as Stephen King, Joyce Carol Oates or David Morall. The story must be realstic, there should be some suspense involved, unnatural events, unexpected twist. Give more importance to disturbing qualities rather than fear factors. Make stories from urban legends or myths. I had read that the story of Mary Shaw from the movie “DeadSilence” was inspired from an old urban legend of Bloody Mary.Try to add details that can create fear in the readers heart.