This question is generally related to ghost or horror stories, but what I was wondering is if there were any lessons (books, tips, etc.) on "subtlety". How to decide what facts to put in and what to omit, for the best effect (discomfort, fear, surreal feeling, etc.). Are there any such helpful resources? Or is it truly just trial and error? Are there some specific works I could look to that are good examples? Any suggestions would be appreciated.