I agree, Its all about the bug list. Think of all the things that bother you or dont make sense in your every day routine and think about how it should be done ideally. The solution is the beginning of a startup.
Yes, keeping a journal is key. The habit of acting upon your ideas- even if it's something as simple as writing them down-, stimulates your brain to give you more. Also, you can stimulate your creativity and get new ideas by trying to combine existing ones at random. It's harder to escape the block if you are in front of a blank page.
Oh, and keep a running list.