I’ve read several bits of writing advice that go something like this: if you know your characters, they will direct the plot. As long as you have a good feel for who your characters are, their responses to various situations will show you which direction to take the story next. As a general rule, I’ve found this to be good advice.
In a character-driven story, the forward action of the story is dictated by the kind of person the character is. Unlike a plot-driven story, removing a specific character and replacing them with someone else would make the story fall apart. For example, in the plot-driven Lord of the Rings, replacing Gandalf with a different good wizard wouldn’t change the overall story arch. But replacing Ender Wiggin in Ender’s Game wouldn’t leave you with any story at all.
What kind of story do you tend to write? If you’re planning out your NaNoWriMo, which method do you tend to go with? For my NaNo story, I’m starting with a detailed character sketch and a basic idea for where the story might go.