GET KNOW TO THE LAY OF THE LAND
You want to learn how to write a great horror story? Go out and buy every volume of Stephen Jones’s annual Best New Horror anthology, and then read every story. That’s about 10,000 pages of reading. It won’t go down as fast and easily as a click-bait list feature, but when you’re done, you’re going to know what makes a great horror story. Better still, that knowledge will be branded deep, into your unconscious, where it will do you the most good. If horror's not your thing then learn the local customs of what you do like. There are similar collections covering just about every posible genre from highbrow Lit-fie to chrome-plated SF to the filthiest erotica. For myself, quite a bit of what I know about writing short stories. I learned from reading The Complete Stories of Bernard Malamud...and readingit. And Then I went further and read my favorites a third time, making notes in the margins about how he achieved certain effects. To a good sentences is one that sounds like Malamud wrote it.