A group of people in a former writers' group, a bad writers' group---er, a group of people who actually didn't write well---spent hours in meaningless discussion about what was frightening, or how to write 'scary' stuff. Often such a conversation would begin: "What's scares you?"
Of course the answer should have been an easy one. Since everyone is different, everyone is often afraid of different things. Although there may be some universal tropes. What we should have been discussing was how to make character development in fiction more compelling. Why? Because unless we believe in and care for a character, we don't care what happens to that character. Stories are about people.
Some people writing horror make the mistake by starting off a tale by thinking in terms of the payoff, or the scare. They focus on the mood, throwing several stereotypical images at us, pausing after each one to ask "Scared now?.....what about now? Now?"
Not that there's anything wrong with establishing tone and setting immediately, but when tone and setting are the major focus of your writing, you end up with something a modern reader is going to abhor. It's akin to sitting around a campfire while your Uncle Edgar says, "There was this guy, see? And he was on a date and they heard a sound, see? And the guy went to investigate and a hook killed him. See? And the hook is still out there!!! Scared yet?"
Of course, a young child hearing such a description will nod yes. Probably because Uncle Edgar is scary as hell. So is the night. And so are the other kids around the campfire who live to give wedgies after lights out. In this case the fear is driven by immediate survival concerns.
When I want to write a horror story, in my mind I begin with something like : "There's a guy. He's the first mate on a slave ship and he's had a terrible experience in the war. He is trying to live up to his father's expectations and is having difficulty dealing with the cruelty and inhumanity of the slave ship."
That person became Avery Tressler and the story became "The Others," published in the anthology High Seas Cthulhu.
In writing The Ravening I began with by creating this character, and fleshing him out in just a few strokes to get me going.
"Ken Tucker is in the woods, hunting for his family. He is a city dweller, feeling lost in his current environment. He is protective of his family, and devoted, but he knows in the new reality of a society beset by the Zagreus virus, that his current skills as urban dweller and teacher are probably insufficient for survival."
So, what's scary? It's scary that poor Tressler is being locked below decks with the slaves and thing stalking them. It's scary Ken Tucker, insecure family man, is beset by creatures that stalk his family. It's scary because we care and believe.