Your character is chatting with her best friend/enemy/crush. But where are they chatting? What does it look like? You need to figure out a setting, fast. Even if you know they’re at school, what does the school look like? What are the colors of the walls? Which direction is the cafeteria?
The fact is, you usually see more of the setting than you write about. In a recent short story of mine (at least it started short, but is rapidly getting longer) the characters are talking by a window overlooking the school’s courtyard. When I wrote this, I visualized a high school I’d visited – not the one I attend – and the whole place, from color scheme to classroom setup, spread out in my mind. I didn’t write about the school colors, or how far you’d have to walk to get to the cafeteria, but I knew. And sometimes the hidden setting is far more important than the stuff you write about. The more you see of a place, the more real it seems to you, and generally it’s easier to write about. You can say, ‘They turned right’ knowing full well that they would turn right, which is a lot stronger than picking a random direction. And if you need to throw in a detail, you have them all at your command, instead of pulling something out of the air.
You’ll find some places to be more setting-worthy than others. I’ve envisioned my house many times to decide if someone’s window faces the street, or how far away the nearest Starbucks is. And for a reason I can’t quite comprehend, I often picture my French classroom when I write about any class scene.
Knowing your setting is like knowing where you are on the map. It allows you to get your bearings, and set off in new directions. Whenever you write a story, it’s a good idea to start out knowing where you are.