One of the hardest parts of revision is deciding what to cut. Surely the reader needs to know the kind of ear muffs people wore in Buffalo, NY in 1890? Or that one of your characters has freckles and is left-handed? Or what a character’s dental records reveal about their childhood?
Here’s John McPhee’s advice:
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. Forget market research. Never market-research your writing. Write on subjects in which you have enough interest on your own to see you through all the stops, starts, hesitations, and other impediments along the way.
This is just one paragraph from a long, wonderful essay that goes into much more depth: The advice McPhee got as a young writer, the writing exercises he gives to young writers today, and why General Eisenhower didn’t include grapes in his still life painting.