Writing is selection. Just to start a piece of writing you have to choose one word and only one from more than a million in the language. Now keep going. What is your next word? Your next sentence, paragraph, section, chapter? Your next ball of fact. You select what goes in and you decide what stays out. At base you have only one criterion: If something interests you, it goes in—if not, it stays out. That’s a crude way to assess things, but it’s all you’ve got.
-John McPhee, writing in the The New Yorker, on the art of “greening,” or whittling down your writing, and deciding what to leave out.