Welcome to my head
I've found that the best way to begin developing an idea and implementing it is to write about it. Thoughts are completely freeform, while writing necessarily imposes structure on them. It's kind of a rough draft of the specification. Also, it triggers associations--there were a couple of spots in that stream-of-consciousness where I realized things and wove them into the narrative. And of course, writing here in public gives other people a chance to critique, point out errors, and contribute ideas, all of which benefit the project.
That's my particular kind of geekiness.