Authors like Stephen King and Anne Rice have built their careers around horror so much that their names have become synonymous with the genre, making it easy to get caught up in the mindset that you're either a horror writer or you're not. But like any plot tool—romance, fantasy, adventure—elements of horror can be woven into every genre.
Follow me, padawans, for tips on incorporating horror to the best effect in your writing.
CHOOSE YOUR IMPACT
Slasher flicks and franchises like Resident Evil have made blood and guts a common horror theme. Plenty of horror fanatics now consider excessive slaughter and gore the go-to indicator of the genre. But notice that most modern horror books don't rely so heavily on entrails.
This is because, outside of games and film, gratuitous gore really is that: gratuitous.
That's not to say there shouldn't be instances of body horror. They can be quite effective when used as emphasis rather than an every-other-page occurrence.
Readers become quickly desensitized if you maintain this tool throughout much of the work. Speaking as someone who is easily squeamish and spooked, I can vouch for the ineffectiveness of not using this element at the right times. If I'm no longer bothered by the story after a couple pages, something isn't working.
HOW TO: Pace instances of death and gore where it will have the most emotional impact. Did a character go further than their personality led readers to believe they would? Did the villain cross a threshold they previously had not? Did the heroes believe they were winning, only to stumble across a horrific scene that smacked them in the face with reality?
The key to shocking readers lies not in inundating them on terrifying imagery, but in yanking the rug out from under their pleasant illusions.
EX: In the animated Mulan, the newly-minted soldiers sing a jaunty tune about the ideal woman they'd love to come home to. This is abruptly halted by the jarring scene of a decimated village and a massive field of dead soldiers. The reality sinks in: this is war. It's not kind. It does not spare innocents. They may never make it home. Mulan picks up a doll, and the final blow hits: they murdered children too.
EMPHASIZE AMBIENCE AND THE UKNOWN
Most people can agree it's fear of the unknown that drives horror. So why do so many movies and games introduce the monster immediately?
Because they can then rely on jump scares.
Here's the thing: you don't get jump scares in writing, so laying all the spooky cards on the table at the get-go won't do your readers any favors. Just like death or gore, you don't want to overload readers on so many creepy details that they become used to it.
Pacing, as with all story elements, is key. The atmosphere may not be immediately oppressive, but it should become steadily more so as reveals are spaced throughout the tale.
Mystery is a huge part of horror for a reason: the more readers don't know, the more they're apprehensive to find out.
HOW TO: Keep limited perceptions that force readers to discover things alongside your main character (yes, even if that character is the villain). Use subtle cues like scenery, weather, a prickle of your character's skin, a noise—small things that could be written off—and steadily build those hints into reveals that cannot be ignored or explained away.
EX: M. Night Shyamalan's Signs steadily builds a perceived threat of aliens that is only uncovered in full force at the end. Peppered throughout the movie are, well, signs: a radio or TV would behave oddly and emit strange noises, animals would act as if threatened by a predator, a silhouette would flash on a roof at night, and finally (towards the end) a hand appears under the door of a pantry—the first and only definitive evidence of the monster before the big reveal.
READERS HAVE TO CARE TO BE SCARED
It's true that a fantastic atmosphere and plot can spook readers, because we all put ourselves in a character's shoes to some extent. But when too much emphasis is placed on the surrounding world and not the character, it's difficult for readers to feel the stakes—hence, they don't become scared as easily.
Fright is an emotion like any other, which requires a reader's empathy to trigger. We don't cry over characters we don't care about, and we won't feel afraid for characters we're not attached to.
Characterization should receive as much attention as ambience and plot, if not more so. Even when nothing spooky is going on, a well-written character can draw a reader into their web of thoughts and fears until the reader is as tense as they are.
EX: Dean Koontz is my all-time favorite horror writer because he has embraced the wonderful tool of characterization. Koontz often doesn't rely on direct horror, because his characters' minds spook readers before anything happens.
Hesitant, not sure why he was hesitant, Tommy Phan picked up the doll.
[. . .] The black sutures that indicated the eyes and the mouth were sewn with heavy thread as coarse as surgical cord. Tommy gently rubbed the ball of his thumb across a pair of crossed stitches that marked one of the doll's eyes . . . then across the row of five that formed its grimly set lips.
As he traced that line of black stitches, Tommy was startled by a macabre image that popped into his mind: the threads abruptly snapping, a real mouth opening in the white cotton cloth, tiny but razor-sharp teeth exposed, a quick but savage snap, and his thumb bitten off, blood streaming from the stump.
[. . .] He felt stupid and childish. The stitches had not snapped, and of course no hungry mouth would ever open in the thing. - Dean Koontz, Tick Tock