Think of a spooky setting like an abandoned asylum. Then add a strange event, like a door opening by itself. And end with a sense of dread, like a scream in the distance.
One that stands out is 'I heard a child laughing in the empty school at night.' Empty schools at night are already spooky places, and the sound of a child's laughter when there should be no children there adds to the horror. It makes you think about the possible reasons for the laughter. Is it a ghost of a child who met an untimely end? Or is it something even more sinister?
A two - line horror story is effective when it creates immediate fear. For example, 'The phone rang at midnight. It was my own voice on the other end.' This short scenario plays on our fear of the unknown and the uncanny. It gives just enough information to spark our imagination and make us feel uneasy.