In his book, Daily Rituals, Mason Currey dug into Hemmingway's 1958 Paris Review interview:
When I am working on a book or a story I write every morning as soon after first light as possible. There is no one to disturb you and it is cool or cold and you come to your work and warm as you write. You read what you have written and, as you always stop when you know what is going to happen next, you go on from there. You write until you come to a place where you still have your juice and know what will happen next and you stop and try to live through until the next day when you hit it again. You have started at six in the morning, say, and may go on until noon or be through before that. When you stop you are as empty, and at the same time never empty but filling, as when you have made love to someone you love. Nothing can hurt you, nothing can happen, nothing means anything until the next day when you do it again. It is the wait until the next day that is hard to get through.
On how Hemingway composed his work, Currey writes:
He wrote standing up, facing a chest-high bookshelf with a typewriter on the top, and on top of that a wooden reading board. First drafts were composed in pencil on onionskin typewriter paper laid slantwise across the board; when the work was going well, Hemingway would remove the board and shift to the typewriter. He tracked his daily word output on a chart — “so as not to kid myself,” he said. When the writing wasn't going well, he would often knock off the fiction and answer letters, which gave him a welcome break from “the awful responsibility of writing” — or, as he sometimes called it, “the responsibility of awful writing.”