Using the element of time can be very effective. If you set a deadline or a ticking clock situation, like the protagonist has to get out of a haunted place before sunrise, it creates a lot of tension. Every second that passes makes the situation seem more and more dire, and the reader feels the pressure along with the character in the story.
You can also use the power of the unknown. Don't reveal too much too soon. Just give hints about what might be out there. For instance, the character hears a growl, but they don't know what kind of creature it could be. Is it a wild animal? Or something more sinister? Also, create a sense of isolation for the character. If they're alone in a big, empty place, it adds to their vulnerability and the tension of the situation. And don't forget to use short, choppy sentences when the action starts to pick up to increase the sense of urgency.
They build tension by being unexpected. When you least expect it, you hear those footsteps, and it immediately grabs your attention and makes you feel on edge.
The story could build tension by creating a sense of helplessness. In the diary, if the girl is in a situation where she has no control, like being trapped in a haunted place. Also, the pacing matters. If it slowly unfolds events, like she starts to notice a strange smell in the house one day, and then over the next few days, other strange things occur, it builds tension. And the use of foreshadowing, like she mentions a strange dream before the real horror starts, can also build tension.
One way to build tension is through pacing. Slow down the story when something spooky is about to happen. For instance, if your character is approaching a haunted house, describe every step, every breath they take. Another method is to use short, choppy sentences when the danger is near. Like 'She heard a noise. It was getting closer. She couldn't move.' This makes the reader feel the character's fear.
Stephen King often plants little hints and foreshadowing throughout the story. These small clues make the reader aware that something bad is coming, but not exactly what it is. And he also plays with the readers' emotions. He might make us feel sympathy for a character and then put that character in a terrifying situation, which heightens the tension.
To build a scary story, start with a normal situation that quickly takes a dark turn. For instance, a family on a road trip decides to take a shortcut through a desolate area. Suddenly, their car breaks down. As night falls, they notice strange lights in the distance. One of the family members goes to investigate and doesn't come back. The remaining family is left in the car, hearing strange growls outside, not knowing what's out there waiting for them in the pitch - black night.
One classic element is a spooky setting, like an old, abandoned house. The creaking floors and peeling wallpaper can create an instant sense of unease.
Footsteps create tension by making the reader wonder who or what is approaching. The mystery builds suspense.
Tension can be built by introducing unexpected twists and turns. Maybe a trusted ally betrays the protagonist or a seemingly easy solution turns out to be a trap. Additionally, ratcheting up the stakes for the characters makes the story more tense.
You can start by creating a sense of uncertainty. Make readers wonder what's going to happen next. Also, build up to important events slowly to increase anticipation.