Where do story ideas come from?

Many people ask this question of people who write. They ask all the hugely popular authors, they ask all the little authors, they even ask the novices like me. It seems like one of those amorphous questions that you can't really get a handle on. I think the answer isn't "where" you get your ideas, it's HOW you get them. I think it really is a matter of training your mind to think in a certain fashion. I read a great book one time, a book called "What if". I think that those two words pretty much sum it up. Writers tend to look at the world different than other people. They are more sensitive to things than other people are. Just put "what if" in front of a lot of things and I think you can generate a lot of possibilities. For example, what if the moon began to fall from the sky, or what if the earth stopped revolving. These of course are outlandish examples, but surely I am not going to post my "good" ideas, I'm not crazy! :) Yet. Feel free to post any methods you might use to stir your imagination. If you've ever gone to a writer's conference, they have all kinds of exercises to invigorate your imagination. Some are good and some are crazy. I'd like to know what you think.