I read or watch something completely different from what I'm writing. If I'm supposed to be writing romance, I go find the crudest comedy in my dvd collection. When I had a memoir writing assignment, I dove through my collection of sci-fi and fantasy books.

Or I just get out of the house. Go grocery shopping or take a long walk and just look at EVERYTHING. Birds, kids playing with the hose, someone's dad climbing on the roof thinking he doesn't need to hire a professional...etc.