Write a scary story in which you explore at least one the following terrors:
- feeling trapped
- paranoid
- afraid of the dark
- emotional shock
- freakish natural event
- the most frightening experience you have ever had
- a wicked mother in law, a scary mansion, a midnight walk on a wooded path, an abandoned school …
- ghosts
short_story_rubric
Read some ghost stories:
http://www.gutenberg.org/files/15143/15143-h/15143-h.htm
Read some more ghost stories:
http://www.gutenberg.org/files/17893/17893-h/17893-h.htm
Have a look at all these horror tropes:
http://tvtropes.org/pmwiki/pmwiki.php/Main/HorrorTropes