Anatomy of a Paper: Part I, Inspiration

How does theoretical physics get done? I had my first exposure to research doing observational astronomy as an undergrad; it was fascinating, following the process all the way from spending freezing nights at the telescope collecting photons, to reducing the data, seeing what the light curves taught you about the stars, to finally writing a paper. But I knew all along that I really wanted to be a theorist. Looking at those papers with their incomprehensible Greek indices filled me with anticipation for the day it would all finally make sense. (Eventually you realize that more and more of it does make sense, but it never all makes sense, or anywhere close. Most of your time is spent thinking about the parts you don't understand.) But I had no idea how such papers were actually produced -- where did you start? When I was looking at grad schools, I took ...