My technique doesn't really help anyone if you're already mired in one, but my solution is to always have a number of pieces that I'm working on at the same time.  That way, I'm rarely faced with a complete blank slate; there's always something that I can keep my hands busy with until actual inspiration strikes.  Just being able to work on something, even if it's as minor as doing some shading on a drawing, can often spur me to get through a day of drawing that otherwise wasn't going to happen.  It also takes the pressure off of me to come up with a new design, which will occur to me eventually if my head's in the game.

And, like a lot of other people, I read a lot and drink a lot of coffee.  If you're putting ideas into your head and get all jacked up on caffeine, something's bound to happen.

c.