Rather than flatly describing sights, sounds and smells, provide contours by showing us the emotional responses of your characters as well.
From A Game for the Living by Patricia Highsmith:
The boy nodded and licked his thin lips. The sight of his tongue near the soft moustache was peculiarly disgusting to Theodore.
An entirely irrelevant detail of the boy has become a character trait for Theodore, and we can feel an unsteady current in the subtext.
[This is the first in a new mini-series of tiny tips for writers; those little insights into the things that make fiction believably real. Those forgettable details that make the fourth wall melt away, drawing the reader into the world of the book, as imagined by the author, but without feeling the author, without being clever.]
For every interaction, there is reality in failure, in minor conflict, in minor obstacles.
At a cafe advertising an all day breakfast.
‘Sorry, we’ve finished breakfast,’ the waitress says. ‘Today’s the day we change the oil.’
Not a huge problem, in the usual scheme of things, so the only possible explanation for this (otherwise redundant) piece of minor conflict is that it must be true. And if that was true, then the fiction around it must be as well.
For even greater reality, slip one tiny extraneous detail into the scene.
The cafe is called Tiffany’s.
Cute. You could have Breakfast at Tiffany’s – if not for the changing of the oil. And those two details make the fiction.