While I think that necessity and deadlines can help give the muse a kick in the pants, it's hard to just sit down and come up with a solid idea for a story. The trick is to recognize these ideas when they happen.
For example, today a time-killing conversation turned into an idea for a novel. Few things are more exhilarating than realizing that, by God, I may have an idea for a new book! It's sort of like a cross between one of Lucy van Pelt's "That's it!!" moments and Gene Wilder in Young Frankenstein screaming: "IT! COULD! WORK!"
Now, granted, an idea is just that - an idea. It still needs characters, a story, various arcs, etc. Plus this one takes place during World War 2 so I'd have to do (groan) research. And of course, not all ideas pan out (though even non-starters are worth it for the practice). Still, no matter what happens I love the "lightbulb goes on" moment and the fact that it's so random. Frustratingly, beautifully random.