Well, start with a creepy setting and build tension slowly. Add unexpected twists to keep the readers on edge.
First, you need a strong concept. Then, focus on creating vivid characters that the readers can relate to. Also, use descriptive language to set the scary mood. Don't rush the story; let the horror unfold gradually.
For writing short horror fiction, think of a unique monster or evil force. Make the protagonist vulnerable. Build up to a terrifying climax and end with a lingering sense of dread.