William Gibson's writing advice comes down to a refusal: he doesn't outline, and he doesn't want to know how a novel ends before he starts writing it.

The Direct Answer
Don't outline. Discover the story the way a reader eventually will.
Gibson has said writers who work out their plots in advance in full are close to incomprehensible to him.

The Novel as Its Own Shopping List

Gibson has compared his process to a violin maker who starts with a piece of wood and carves away everything that isn't a violin, except he's generating the wood at the same time he's carving it. He doesn't begin with a plan and doesn't like knowing the ending in advance, saying that not knowing keeps the exploration alive. He shares this instinct with Elmore Leonard, another writer who avoided plotting too far ahead.

This shapes his revision process too. Instead of finishing a rough draft and fixing it later, Gibson starts at page one and revises through the whole manuscript again each day, which means the opening chapters of a Gibson novel get rewritten far more than the ending does. Once a book is finished, he says he almost never changes the opening sentence again.

Characters First, Ideas Second

Gibson has also been direct about where his fiction actually comes from.

I don't write novels to express ideas; I write novels about characters and the ideas come out of them.

William Gibson, interview with IndyWeek, 2010

That ordering matters. Gibson isn't building a world to prove a thesis about technology. He follows a character and lets the implications surface on their own, sometimes not recognizing what a book was actually about until well after publication and interviews force him to articulate it.

For the daily schedule and revision habits behind this approach, see the complete William Gibson writing routine.

What You Can Steal