Truman Capote wrote lying down, as did Marcel Proust, Mark Twain, and Woody Allen.  

Capote started with coffee, then switched to tea, then sherry, then martinis, as the day wore on. He wrote his first and second drafts in longhand, in pencil. And even his third draft, done on a typewriter, would be done in bed—with the typewriter balanced on his knees.

Charles Dickens, Winston Churchill, Virginia Woolf, Ernest Hemingway, Philip Roth, Lewis Carroll, Thomas Jefferson, Fernando Pessoa, and George Sand all wrote standing up.

Roald Dahl wrote in a shed. 

Philip Pullman used to write in a shed, but eventually gave it to an illustrator friend.

Umberto Eco has a converted church as his scriptorium. One floor has a computer, one has a typewriter, one in which he writes long-hand.

Dashiell Hammett published nothing after he was 39 - he felt he was repeating himself but never managed to find a new style he felt was good enough.

Ray Bradbury wrote an early version on Fahrenheit 451 in nine days on a rented typewriter in the UCLA library basement.

J.D. Salinger often worked in the nude.

Will Self uses a wall of Post-It notes to plan and structure his writing. 

Elmore Leonard wrote on yellow legal pads. 

Arthur Hailey spent 1/3 of his time researching, 1/3 preparing, outlining and publicising and 1/3 writing... no more and no less than 600 words a day (three pages). He did not get things wrong. His preferences might show; but his facts were correct.

John Steinbeck special ordered round black pencils.  He only liked to write with sharp pencils that made dark marks on the paper.  Steinbeck hated writing with short pencils, so after his pencils got too short he would give them to his son to draw with.  Steinbeck also said that he required a 4 to one dawdling to work ratio.

Joyce compiled notebooks full of puns for Finnegans Wake, and when he started each new section he'd write a simple first draft and then go back through all the notebooks, identifying puns that fit into that section and crossing them out with colored crayon. (The notebooks survive but the labor of reconstructing their use has barely begun.)

Haruki Murakami commutes into a city apartment in Tokyo where he writes.

After the publication of Joe Gould’s Secret, Joseph Mitchell came to the office at the The New Yorker magazine almost every day for the next thirty-two years without filing another word.

Michel Faber corrected the first manuscript of The Crimson Petal and the White with house paint.

Gustav Hasford was a serial hoarder of very overdue library books, and had 10,000 of them in storage lockers.

Don DeLillo types each paragraph onto its own sheet of paper, so that he might concentrate better.

Gay Talese would pin pages of his writing to a wall and examine them from the other side of the room with binoculars.

Jonathan Safran Foer has a collection of blank sheets of paper. 

Cormac McCarthy said that his perfect day is sitting in a room with some blank paper.

Ethan Canin copied John Cheever paragraphs out to learn what made the man's writing tick.

Anthony Trollope required of himself two hundred and fifty words every quarter of an hour. 

J.G. Ballard, a fan of discipline in writing, prepared very long outlines, and aimed for 1,000 words a day. 

Walter Benjamin advocated delaying writing an idea as long as possible, so that it would be more maturely developed.

Richard Ford and his wife took a gun and shot a book by Alice Hoffman, after she had given his book Independence Day an unfavourable review.

Vladimir Nabokov wrote most of his drafts on index cards so that he could shuffle them about and carry them along with him on his butterfly expeditions. He kept blank cards under his pillow for whenever inspiration struck.

Benjamin Franklin and Edmond Rostand are among the famous authors who wrote while soaking in a bathtub.