When I think about a scene, I think about what the characters are doing. How they interact with each other, their vulnerabilities and their personalities and their wit or depth. That's usually always what springs to my mind first. I love characters.
But something else that's important - very, very important - are what the characters are doing. When you talk to a friend, you don't just stand there and talk. You bite your lip, take a sip of your drink, play with a pen, put your hair behind your ears, nod your head, smile, put a sweater on. People are animate. So it's important you not only know how your characters interact, but what they're doing and where they are.
One of the exercises Megan had me do was write a description about a room. Not just a general description, but include every facet of it. Obviously, a book with every facet of every room the characters are in would be very, very annoying. But take this picture for instance:
If I were to describe it, I could talk about the bed or the splotches of paint on the wall, looking like a kid on an acid trip blew a wad of paint bubbles. It looks like a kids' room definitely designed by an overzealous adult. This could be the room of a teenager who hasn't had the design changed since she was a toddler, right? I could just have my characters in a room sitting there talking, but I could bring that scene even more to life if I set a picture for the surroundings. If I plant them in this room - one playing with the
stuffed elephant, Ellie, on the bed; one drawing back the pink drapes and watching a thunderstorm while talking about her sister's sickness; the other sitting on the floor and flicking the abstract lamp on and off, absentmindedly listening - things get more interesting.
What I'm trying to say is, a setting needs characters and characters need a setting.
That room would just be a paint-spotted kid's room without characters to fill it with life. And those characters would just be people, not bringing their life into a setting that highlights their personality. Settings just making everything more...realistic. And making words seem like they're alive, with fictional characters becoming real, is one of the most beautiful things about writing.