In my own work, when I start off writing a scene, I don’t know which physical details are going to turn out to be meaningful. But, inevitably, certain images will stand out—you start to decide which ones are important as you go. When I’ve put an image in and it seems to be working, that's always a sign to me that I should go back and ask myself what it is about that image that grabbed me, and whether I can dig deeper into that, make it mean something more.