I often try a change of venue or method. I change from computer to handwritten, I go to a new place I've never been to (i.e. new library or coffee place). I also try leaving it alone and refusing to think about it, as in when I find myself thinking about it, sing annoying earworm songs to get it out of my head. perversely, then my brain insists on attacking the problem, and it just rushes out. Gotta really mean it, though.