Which Came First, The Idea or the Egg?

I've always been interested in other writers' processes and the journey by which they go from idea to finished manuscript. Of course, I realize what works for them won't necessarily work for me, but a little experimentation could be an excellent book starter, especially if you're of the procrastinatory (is that a word?) persuasion. Typically, I start with a scene that's popped into my head for no apparent reason, possibly the result of a chance phrase I've heard or a clip from a movie or maybe even dementia....whatever. I then build around this paragraph or so I've scribbled down, gradually getting to know my characters and where the story is going pretty much as I go. And what, you might inquire, has this process netted me thus far? I'm so glad you asked. I have three partially finished books cowering beneath my bed and one finished, though highly unpolished, manuscript locked in a closet refusing to come out until I give it something pretty to wear. Drama Queen. Obviously, this isn't working for me at all. I firmly believe there is no set in stone "right way" to write a novel. However, there are many "wrong ways" to do so, or at least wrong way for me. The above scenario is a perfect example. In someone else's hands this could work perfectly. Alas, I'm not someone else. I'm just little 'ole me and I need to figure out a way to work with that. Presently, I'm involved in some serious prewriting for my new book. Usually, this merely involves a list of each character's physical description, their families, a half-hearted stab at their past histories, etc. I know, I know. Lazy writing won't get you anywhere. As I mentioned in my last post, I've started with the worldbuilding before even trying to flesh out my characters and what makes them tick. To my surprise, the worldbuilding has actually helped my characters to start taking a more defined shape. Motivations and conflicts are springing up almost on their own from this world I'm creating. ::slight pause while a loud round of "Doh!"s are heard round the blogosphere:: Okay, okay. I deserved that. Better later than never, right?