I've been working on the outline to my story using a combination of the snowflake method and the phase drafting method and it's been a lot of fun. Even though I've already written the first draft of the story, the outline is helping me to flesh out characters and scenes that are wimpy, and is drawing my attention to plot holes I didn't see before.
What I've discovered: A character's motivation is EVERYTHING! You can't just have a character do what you want them to do without having an explanation as to why they would do such a thing. Outlining helps me to see further ahead. If there's an action that's essential to the plot, I need to make sure whatever character is going to perform that action has the kind of personality and motivation to take that action.
For instance, in my story the villain ends up becoming extremely powerful, escapes, and then purposefully performs an action that will kill him within 48 hours. I had to figure out a motivation for him to do all of these things.
1. becoming extremely powerful: He's trapped on a planet and needs the power to get back home, thus he's highly motivated to gain power, even if it means becoming a murderer.
2. escaping: It's not how he wanted to leave, but he is strongly motivated by the group of law enforcement ninjas who are going to kill him if he doesn't leave his entire plan unfinished and left behind.
3. drinking poison: This is the most complex motivation of them all. There are several reasons he's motivated to do this, but the biggest is that he's a sociopath who unwaveringly has to accomplish his goal at any cost. He does this. As soon as his goal is accomplished, he doesn't care anymore. For him, the completion of the goal is what mattered more than getting home.
Now, if I were to create such a villain and have him be even keel emotionally, or unflappable, and suddenly show that he has an obsession with completing goals, it wouldn't work. But because I know what his final motivation will be, I can plant seeds early on about how the villain has a deep-seated need to complete goals regardless of any consequences or cost.
I'm hoping the reader will get to the end and be surprised, but still be able to say "I should've known that was coming."