Mantel handed out advice the way she wrote, plainly and with a little edge. Her ten rules for fiction, published in The Guardian in 2010, run from the practical to the deep craft of where to aim a scene. A few of them are worth stealing whatever you write.

The Direct Answer
Write a book you'd actually want to read, aim your energy at the point of change, and step away from the desk when you're stuck.
Her core advice comes from ten rules for writing fiction, published by The Guardian in 2010.

The Ten Rules, Boiled Down

In 2010 The Guardian asked a range of novelists for their rules of writing, and Mantel's list has outlived most of them. It opens on a practical note, telling anyone serious about the work to get an accountant, then points writers to Dorothea Brande's Becoming a Writer with the instruction to do what it says, including the tasks that look impossible. The rule people quote most is simpler than either.

Write a book you'd like to read. If you wouldn't read it, why would anybody else?

Hilary Mantel, The Guardian, 2010

She also told writers to work like a magpie, collecting images and phrases wherever they turn up and recording them on cards or in a notebook. Inspiration, she said, takes constant vigilance, so you stay on the watch for material day or night, awake or asleep. It's the same instinct behind the notebook she kept by her bed. She was just as practical about openings, warning that anything placed before chapter one may get skipped, so a vital clue doesn't belong there, and that a first paragraph can often be struck out without any loss at all.

Aim at the Point of Change

Her sharpest craft advice is about where to put your energy. Concentrate the narrative, she said, on the point of change, the moment a character arrives somewhere new or the world shifts around them. That's when you step back and fill in the details of the setting, because that's when the reader actually needs them. She flagged it as especially important for historical fiction.

Description had to earn its keep too. Mantel warned against ornament for its own sake and preferred description that comes through a character's eye rather than from some godlike overview, so that noticing becomes part of who's doing the noticing. And when a scene jammed, her advice was blunt: get away from the desk. Take a walk, run a bath, go to sleep, make a pie, do anything but sit there scowling at the problem.

For how these ideas played out in practice, see the full Hilary Mantel writing routine.

What You Can Steal