Another method I've adopted includes carrying a thin, black Moleskine notebook and a pen around with me wherever I go. Its about a fifteen minute walk down to class for me from my dorm room, and on those walks I typically find my mind wandering. I'll come up with great ideas or think of something that I want to do or see someone wearing a jacket or a pair of boots that I absolutely need and usually those ideas disappear when I reach my destination. As a remedy for this insult to inspiration I've started jotting such thoughts down in a notebook. I don't stop in the middle of the sidewalk or anything, but I do find that it helps to have a physical form to jot the ideas down in always on hand.
One such list: Favorite Words