From his blog:
1. Find the time of day when you do your best thinking — when your intellectual energy is at its highest — and set that time aside for writing. (If that’s impossible because of work or other responsibilities, then find the best time that’s available to you.) Then preserve that time. Be flexible and generous all the other hours of the day, but be rigid and ruthless about your writing time.
2. Write to think. Don’t try to know where you’re going before you start writing, but write to find out what you think, or find the story you need to tell. Never expect that a particular time-unit of writing will produce a given number of publishable words. You must learn to think of your writing time as a period of discovery, in which you find out what you think, or what images and rhythms tend to emerge from your mind, or where a story seems to want to go. If you focus on discovery, then something worth sharing with others will emerge, in its own way and on its own schedule. But that’s not the kind of thing that can be forced. Allow yourself the freedom to explore.