I think Steven King always says “Wal-Mart.” Harlan Ellison says “Poughkeepsie.” Lawrence Watt-Evans has a good essay about this. So does Tim Wynne-Jones. And Justine Larbalestier has great advice as well.
As you can see, this question is the one every writer hates and everyone always asks. The fact is, ideas come from all around you, from everything you experience every day. You see a light on in an abandoned building and you think “I wonder who’s in there and what they’re doing?” The answer to that is an idea for a story. Whether it’s a good story or not is up to you.