Problem: Invaders are doubling their efforts to take over my main character's homeland. At the same time she is struggling to understand a power that is nothing like it should be, and is a disappointment to her parents. This shows both the inner problems she is struggling with and the exterior one she is forced to deal with going on around her.
Stakes: Invaders are not only driving her people from their land and taking over, they are wiping out her kind because they believe they are evil. If she can't figure out her errant power and discover a way to control it and use it, she may have to fear for not only her family's land, but her life. Again this shows the inner and outer stakes.
Solution: She must find a way to harness her power so she can use it to help her people fight back the invaders. In the solution the two combine, but this isn't always the case.
Once you know these three elements, you know the core of your plot. These are also the three elements that are found in a good one sentence log line. I've found that in knowing these elements, and writing my one sentence log line ahead of time, it helps me hone in on my story from page one and not lose focus on it. How do you make sure your story has the necessary elements?
These elements are taken from my historical YA fantasy that is due out by Compass Press in early 2013.