Open Culture has compiled seven pieces of fiction writing advice from Ernest Hemingway. They all look pretty good, but the pencil one is especially near to my heart.
6: Use a pencil.
Hemingway often used a typewriter when composing letters or magazine pieces, but for serious work he preferred a pencil. In the Esquire article (which shows signs of having been written on a typewriter) Hemingway says:
When you start to write you get all the kick and the reader gets none. So you might as well use a typewriter because it is that much easier and you enjoy it that much more. After you learn to write your whole object is to convey everything, every sensation, sight, feeling, place and emotion to the reader. To do this you have to work over what you write. If you write with a pencil you get three different sights at it to see if the reader is getting what you want him to. First when you read it over; then when it is typed you get another chance to improve it, and again in the proof. Writing it first in pencil gives you one-third more chance to improve it. That is .333 which is a damned good average for a hitter. It also keeps it fluid longer so you can better it easier.