What are Shelley's criteria for a good ghost story?

In some case if you already have a main character, she could be briefly shown throughout the story. Use her lack of appearance to serve a plot twist at the end of the story. She might be a neighbour that comes over every so often, she seems really nice ... with a creepy feel. She's always baking and making treats for others, she has noticeable facial flaws but doesn't interfere with her personality.