Don't Explain How Things Are Linked in Fiction

Never, ever, write "As X happened, Y started to happen" unless there is a direct cause between the two. There's no need to explain how things are linked in fiction. "As John looked out of the window, Mary started to chop the tomatoes" is always inferior to "John looked out of the window. Mary started to chop the tomatoes." A simple point with profound ramifications about the writer's responsibility to the reader's imagination.