There’s a discussion on Quora about the best ways to overcome writer’s block.
Lots of good tips, ranging from the practical by Matt McDonald:
Learn to type quickly: I find that if I can write as fast as I can think, that helps the transition from my brain to the page.
Write in your voice: This is a speechwriting bias, but I always write as I (or someone else) would speak. I don’t try to have a different voice on paper than I would have talking with a friend.
To the philosophical by Andrew Brown:
When I’m really motivated to write but don’t have anything to write, I turn off everything (computers, phone, music, sometimes even the lights) and just sit in silence, not unlike meditation. I let my mind wander wherever it wants, and it usually ends up somewhere strange, interesting, or otherwise crazy. Once I get the urge to write, I bottle it up, thinking it through for another couple minutes both to build anticipation and to clarify my thoughts, and then start writing.
Personally, I’m of the “relax and just write” persuasion. Even if it’s “I don’t know what to write. I don’t know what to write. I don’t know what to write.” over and over again. As Merlin says, you have to make the clackity noise for writing to have any chance of happening.