I've kept a notebook since 1976. It has every peak that I've climbed, the technical climbs, and a few long endurance races. I have usually included the peak, elevation, partners and whether the summit was tree covered or bare for the Eastern peaks. For technical climbs it includes the number of pitches, the YDS difficulty and the grade. For really meaningful ascents I have included other editorial comments, and on a few I've noted first ascents where applicable.
It is on the extra pages of my third grade math spiral notebook and has a duck stamp that I got for getting a problem set entirely right. It also has a partial list of my Presidential Physical Fitness results from 4th and 5th grade.
There are a lot of memories in that book...
Best of luck in your own efforts.