Write as if in a trance. Always say ‘yes’ and write without censoring. Don't block anything. Hold the door open for your self to surprise you.
Only the next sentence matters, not the last. You can always go back and edit, but in this moment, all you need to do is to move forward.
Mix handwriting with typewriting. Go backwards and forwards. Write the first draft on the computer, then write it out by hand. I find that in the gap between the two sometimes magic happens and new ideas are born.