Discussion Panel - Plot or Character, Which Comes First?

I'm starting a new feature for the blog – panel discussions around common issues that authors face.  I think it's a great way to get a unique perspective inside the author's mind and I thank each one of them for taking time out of their busy schedules to participate in today's discussion.
Today's panelists are: Philip Chen, Tonya Plank, Daphne Coleridge, TL Haddix,