For Christmas I got season 1 of the TV show Once Upon a Time. The first thing I watched was the bonus features, because I love seeing how these things are made. What stuck out to me was how many times the writers of the show said "we wondered what would happen if" or "this path was obvious, so we asked ourselves what if..."
The biggest thing to me is when they were talking about Prince Charming's back story. They knew everyone would expect to know his story--the royal prince with a rich father who would take Snow White away. So they asked "What if that wasn't his story? What if he was actually a pauper?" From this simple realization that the story would be more interesting with Charming having a different back story, the show has a whole other plot to go into with the conflicts of becoming a prince without having been raised as one.
As I've been plotting my next book, I've asked myself these same questions. What would the audience expect to happen from this? If it's something good--like the heroine winning, then I don't touch it. But who's expected to be the bad guy? The good guy? What cliches are in this genre that I want to avoid? Then from this, asking "what if this happened?" Sometimes it's awful. But sometimes it's good. And I've found that things are a lot less predictable and a lot more interesting.
Do you have any tricks for plotting your story?