There are times when I can place exactly the moment I get a story idea, and others when the ideas just seem to sneak up on me unexpectedly. The first novel I completed, which was about a radical religious cult...I couldn't tell you what spurred that idea. I remember being bored in Philosophy class sophomore year of college, and then I just started writing a story about a girl with the name of Elizabeth McLancy.
I've also gotten ideas from the news. The first year I crossed the NaNoWriMo finish line, I got my story idea from watching the news one night.
My current project, I can also place the exact moment I got my inspiration and where it came from. I was on a walk, listening to one of my favorite podcasts--Smart Mouths. They were talking about the earthquake in Haiti and what teenagers were doing to help, how wonderful it was that teenagers were stepping up and donating money through text messages, using something that they're usually made fun of doing all the time and turning it into something good.
One quote in particular stood out to me: "Our generation's gonna kick ass."
It was all downhill from there. I'm now querying that novel, and working on revising its sequel. And it all started with a podcast.