I have separate little notebooks for exposure and developing. Beyond what was already mentioned, I sometimes use hyperfocal focusing, and I sometimes "hedge" by 1/2 stop or more from the markings on the lens, so I write down how I focused ( incl if set to infinity. ) Also, I'm usually trying to think about what I'll be doing to print, so I will make a note about what I intended for a highlight or a shadow area, and I almost always make a note about the thought process of my metering ( e.g. set at shadow +2, or highlight -1... )

Like someone else said above, it probably depends on what you are trying to accomplish. I'm trying to do well with my exposure and the notes so far have been very helpful in homing in on what works for me. I probably don't need notes anymore for my F3 for hyperfocal because I've developed a very good sense of how much I can do, but I still don't have a handle on DOF on my folder and some older cameras so I'm hoping the notes will help.