The Paris Review interview of E. B. White has several good passages about writing. Here's one:
Delay is natural to a writer. He is like a surfer—he bides his time, waits for the perfect wave on which to ride in. Delay is instinctive with him. He waits for the surge (of emotion? of strength? of courage?) that will carry him along. I have no warm-up exercises, other than to take an occasional drink. I am apt to let something simmer for a while in my mind before trying to put it into words. I walk around, straightening pictures on the wall, rugs on the floor—as though not until everything in the world was lined up and perfectly true could anybody reasonably expect me to set a word down on paper.
(via Brain Pickings)