I keep a "quilt journal". Every quilt I make, I record the pattern, where I found/bought it, the fabrics used and where purchased, what inspired me to make that particular quilt, and if it is a gift and for whom. I also take photos of the top and back and add these to the journal. I have a section for projects that I want to make, UFO's and why they have become UFO's (sometimes revisiting this section re-inspires me and the UFO becomes a finished quilt). Rereading my past journals it is interesting to see how my quilting (or my taste? LOL) has evolved over the past 15 or so years.
Happy Quilting!