One element of world-building I like to emphasize is the need to establish a setting word by word. It isn’t just about creating a time and place for the characters to inhabit; it’s about creating an atmosphere with every word.
For example, if you want to describe something red in your scene using a simile, you might say:
red as a garnet
red as spilled blood
red as rotten tomatoes splitting in the sun
red as ripe strawberries
red as a clown’s nose
Each of these sets a different tone. The garnet suggests jewels and elegance; the blood threat and danger; the clown’s nose humor or absurdity. The ripe strawberries are luscious, but the rotting tomatoes suggest decay and unpleasantness. A narrator describing his new love interest would probably not compare the shade of her lipstick to rotting tomatoes or a clown’s nose ... and if he does, the author is signaling wildly to the reader that something is off about this relationship. Maybe the new love interest is really sinister, or the narrator is, or maybe this is a comic novel that will upend our expectations about romance.
We don’t just build stage sets; we show how our characters respond to their surroundings. Is the elegant restaurant in your story intimidating to the characters, or is it their happy place, or is it a facade for the chaotic back kitchen where your characters spend most of their time? Readers will discover those answers in whether you show fraying threads on the drapes or a spot on the silverware. In the bathroom, hunched over that pregnancy test, what is your character hoping to discover, and how does that eagerness or dread affect the way she inhabits that space? Is the basketball court the place where your character rushes to play and hang out with her friends, or is it a grim endurance test in a weekly gym class? Characters who approach the same place with different attitudes will notice very different details and will use very different words to describe them, and the author’s word choices have the same responsibility.