For me, a scene is ready to write when I’ve got the right feel for the setting. I think it’s what people who talk about movies call mise-en-scene. The way I understand it (I could be wrong), mise-en-scene is when a director goes from the bare bones of script/screenplay to a vision of how the scene will actually look. So, for a writer, when an idea of what needs to happen fleshes out into a full picture.
Maybe I’m conscious of this process because of my personal method of ‘pre-filming’ (as described in GOOD WRITING HABITS). But, however you work, the right setting enhances the action. Or if it doesn’t enhance the action, I’d say don’t bother with it. Description for description’s sake is a waste of space.
There are probably no general rules for what setting will enhance what action. Sure, violent action matches violent, stormy weather—and I’ve done that at the end of Worldshaker. But opposites can work well too, violent action set against a genteel setting. My only rule is, if it feels right, it is right.
If Ferren and the White Doctor, there’s a scene of terrible betrayal, set among green rolling hills in the morning sunshine, green grass dotted with bright scarlet flowers. Maybe I could analyse why green-with-splashes-of-red belongs with that scene, but at the time, it was just a ‘click’. Since it’s the scene that everyone remembers from the book, I reckon it must click for other people too.