Walk into my house at any given moment, and you will find a stack of notes waiting to be filed. These are snippets--descriptions, impressions, overheard quotes--anything that I might want to use at a later date in a piece of writing. Writing doesn't always have to be a big project. Serious writers are always "writing," even when they are not putting pen to paper. It can be as simple as taking a few moments to record something you don't want to lose--that turn of phrase that occurred to you in the shower, that metaphor, that odd name in the obituaries. Obituaries make great character sketches.
I keep a 6x9 file box divided alphabetically as a way to store these pieces, but they stack up around the house anyway. I love leafing through them, remembering what was going through my mind on a particular day.