I jot down lots on my kneeboard. It's the way I was taught -- my instructors were almost exclusively ex-military.
I record freqs, CRAFT, ATIS/AWOS, fuel tank transitions, fuel on each side at that transition, etc. It helps me with post-flight self debriefing -- to learn from my mistakes, what worked especially well, record data into my, gasp, paper logbook.
We all debrief ourselves after each flight, right?