How many times have you picked up a book, only to have every scene happen between talking heads in an empty room? There is no past, no future, there is no background, no scenery, no life - nothing and no one exists outside of the main characters. And for all the character description you're given, you're not even sure they have bodies.
"Setting the Stage" is a technique I learned about from, of all things, Archie Comics. I loved Archie Comics. And one of the things I loved most about them was when things went on in the background.
In my particular favorite, and I don't even remember the main story now, the school janitor began investigating a slow leak in a classroom ceiling. He returned with a ladder, and found the leak had become a trickle. He returned with a mop, only to find the trickle had become a broad stream. He slammed the door shut desperately to keep the water at bay, but the door whooshed open as a tidal wave of water carried him off down the hallway. None of the main characters noticed.
It was great. It was simple. It made the world they lived in seem more interesting. Now the main characters weren't actors on a sterile stage, they were part of a universe.
And that was the purpose.
Many time when we're telling stories, what begins on paper as a couple of characters exchanging boring but necessary information needs to be enlivened. We need to give depth, resonance, show those coveted "telling details," sneak in some symbolism, or distract from a crucial clue and plant a red herring. Sometimes, we just need to make it clear that our characters are in a different room of the house.
That's where these details come in.
I once wrote a short story where a female character made coffee for herself and her husband while they had a difficult conversation about his deceased first wife. The conversation began when she set his mug in front of him, and throughout the rest of the scene they interacted with that coffee in the same way you and I would - they looked into it to avoid each others' eyes, they blew on it, they drank it, they toyed with the handles, they ignored it as they got to the meat of the conversation, and then they went back to it when they reached a stalemate. And when she realized that their conversation was as cold as their coffee, she got up, threw the dregs of her mug down the sink, and walked out.
It was so simple: loaded with sensory details, rife with ambiguity and meaning, and elegantly showing the passage of time - all without once mentioning their awkward pauses or looking at a clock. I had done it by accident, really; simply recording their conversation was as boring to me, the writer, as it would have been to an audience. But giving them coffee worked. It worked because none of us in real life sit and speak without moving. People fidget. And life goes on in the background.
Can this technique be overdone? Sure. When you're trying to move the pace along quickly, to get to that all important show-down or fight scene or the hero's declaraton of love, you don't want to include many of these tidbits because they can slow the story down. But when you want to slow the story down, or when you can spare the time to give the characters and the scene added depth, or when you simply want to misdirect our attention, give it a shot. Your audience, and your characters, will thank you for it.