Card and pencil, course guides with shots and comments noted, course map with compass points shown, various other notes on things such as weather, course conditions, unusual features.
I once worked for a guy with a "photographic" memory and a penchant for throwing out figures and statistics on all sorts of arcane subjects. He was considered to be a braniac and not even the most senior corporate officers would challenge him. A few of us who knew him well and were subject experts often chuckled at how many serious mistakes he made in his pronouncements without any consequences. Only once that I am aware of was he ever called on an error- when he missed the annual U.S. corn yield forecast by three or four zeroes- but that didn't seem to impact his credibility nor his compelling need to rattle off figures.
Not to say that some people don't have these skills. Cirba and Childs certainly seem to. A former golf colleague not only could remember what shots he hit on a hole of a course he played for the first and only time five years before, he could tell me what I hit and where I ended up. It was trully amazing, and I never found him to be wrong.
As for me, I remember generalities without notes, but not specifics and small details. To reflect with any degree of accuracy, I have to put myself in the moment and consult with my notes and other tools.
BTW, I blame my notetaking and preoccupation with the design, presentation, and conditioning of the course for my game going to hell. It is probably a poor excuse at best, but that's all I have left given that I am okay physically and I remain on a very slippery slope.
Actually, I also blame Mike Cirba for his observation that gca.com may make us into better golfers but worse players (or something to that effect). There is no way to quantify and disprove the former, but honest handicaps and the spankings I've taken by the likes of Huckaby and Swanson don't refute the latter, at least in my case.