Definitely taking pics is the place to start. I put mine all in one folder on my computer, sorted by date, so I can just browse.
...Of course, I regularly have disasters happen. YLF is my only source for seeing all my old outfits before... this past December. Haha! My whole fashion history! Yeah, my car was broken into and I lost my memory sticks.
But anyways, I'll go through WIW threads to see my own past outfits and those of others. Sometimes people do a compilation, bringing things together in one thread.