This is how we do it… [sing]

Sol said (in comments): “How do you do it?
Well, Zelazny’s method works very well for some: every time you flip over to the screen where you’re writing, you have to promise yourself that you’ll write at least three more sentences before you leave that screen, basically.
For me, that probably wouldn’t be enough… somewhere in there, something has to kick off and make something more of itself. What I do is commit to getting 500 words out every time I start writing — by the third time I write that day, I’m getting close to the 1800 I want, per day. Here’s a few other bits…
– Never edit: If you want to spellcheck, that’s good, but the next run is for editting — people get hung up trying to make one page perfect (rearranging sentences and scenes) instead of writing more imperfect pages. It will never, ever be perfect, so write like crazy and edit later. One of the best things keeping the word count going is that you have to force yourself to accept what goes down on the paper as your first draft, good or bad, and move on.
– Embrace productivity, not perfection: it doesn’t matter if what you’re getting down is crap, it’s your crap, and by god there’s a story there somewhere. Eventually you’ll find it, but for now just write write write. Nobody writes a perfect book, certainly not the first time. Stephen King writes 60k words a month so that after he does his second draft he’s still got 54k.
– Take lots of showers: Seriously. Something about those water drops hitting your head make ideas come.
– Never write everything: Finish each writing session with something you still haven’t had a chance to write lingering in your head. Let that small bit you haven’t done sit there and fester germinate. By the time you get around to writing that part, it’ll have lots of little word buddies that are waiting for you to write them as well.
– If you don’t know what comes next, move: You’ve got lots of characters (and if you don’t, add some, or make your main character schizo, or something). When you’re stuck on what happens next to character A, move to character B: someone else that you DO have an idea about. Readers will think you’re building suspense and heightening anticipation — they’re dead wrong, but who are you to correct them?
There are lots of people who know more about this than I do — these are just tricks for getting the words out there. Everything after that is gravy, so wallow around in the keyboard and just push. :)
Update:
Chris Baty’s suggestion: “Keep those guilt levels high and stay away from that delete key.”