A couple of good ways to brainstorm a story is through plot and character. Whether plot or character comes first when composing a novel is sort of like the chicken and egg thing. It greatly depends on the author’s point of view. Plot and character are so entwined that it’s often hard to even separate the two. Like all elements of a novel—dialogue, exposition, description, pacing—plot and character are woven throughout. I think writing can be compared to weaving, where the threads are blurred within the composition of the overall pattern.
After several books I’ve found that, although there are guidelines to writing, there are no hard and fast rules. That’s why the best authors appear to break them.
For me, it's nice to know where I’m going before I create my characters, even if it’s only a general idea of the plot. Once I have my external conflict (plot) I can then create the characters who would suffer the worst internal conflict within the story. So, if I have a storyline where the heroine must leave her village to find her missing father, who is tangled up in all sorts of political intrigue, I will create a character who is not an adventuress at heart. She’d prefer a cozy, quiet life of knitting and cooking and raising babies. The last thing she would want is to leave her peaceful home and go wandering about the dangerous countryside, eventually becoming tangled up in the same intrigues that cost her father his life. Her internal conflict will be so much greater than creating a character who longs for adventure and excitement. And her growth would be much more rewarding and life-altering. And this is exactly what I did for book two in The Elven Lords series, The Lady of The Storm (releasing August 2011).
Once I create the characters, and plunk them into the story, they will take over, sometimes changing the plot drastically from what I’d first envisioned. And I let them. Because isn’t that the magic of writing, when the words aren’t coming from you, but the characters that you’ve created?
So should you try starting with plot or character? That’s all up to you, and the story you envision writing. But if you’re not quite sure, try starting with a general plot outline or idea, and create characters who would hate to be put into the situation you’ve created. Or start with a fascinating character, and create a situation that will challenge them. And see where the magic takes you.