Personally, I just write. I write pages and pages of stream-of-consciousness thinking about the application, everything from how it will look to how the backend

Personally, I just write. I write pages and pages of stream-of-consciousness thinking about the application, everything from how it will look to how the backend will function to how it will make money. Once I'm done with that, I sleep on it (as it's usually 5am by that point), and the next day work on mockups and DB schemas if it still seems like a good idea.