From Jody Cleghorn of Write Anything. [This site is now closed, but the content remains online as an archive.]
Make up the rules for what you want to produce.
Try to write every day, even if just for a few minutes. [Substitute ‘paint’, ‘sculpt’, ‘cook’, for ‘write’.]
Work on several projects. This keeps you energized and working creatively even when one project isn’t firing. [Good advice, but I’m guilty of taking this a little too far. Make it manageable.]