Some people are organized, detailed and methodical with plotting out their stories.
Others, like me, are not.
That's why I found this plotting tool so very helpful. It allows freedom for the story to take different turns and twists, all while keeping a strong structure. I found this on Karen Harbaugh's site a long time ago (the article about story structure).
Basically, there should be four major decisions that happen in your book. The first two lead up to the third, which brings about the black moment (or the climax). The fourth decision leads to the resolution (or the HEA).
I actually draw a circle, just like Karen recommends, and mark the four points and what my character's projected decisions may be. Karen's article is great and I really encourage you to read it, especially if the middle of your book seems to fall flat or get boring.
How do you outline your stories?