I keep track of temp, weather (sunny, cloudy, humid, rain, etc), tire pressures, tire wear markings, suspension settings, turn by turn reference points (braking, turn in, apex, exit; visual stuff - sometimes where to look like, "keep looking as hard as possible through corner until you see X off the side of the track"), shift points, overall feelings for the day and feelings turn by turn, things to try turn by turn (changing reference points, line, whatever), and anything that I feel that I need to work on overall. Sometimes you just realize that overall you need to get off the bike more, get your upper body lower, look further through all turns, etc.
This gives me a reference for the condition of track, condition of my tires, how I felt physically/mentally, what lines/techniques worked/didn't, what things I saw/felt that I want to try to improve each turn, and what things I saw/felt that overall need work. They are good reminders for things to focus on the next time at that track, and somethings for the next time at any track. I find it really helps to be able to put into words what you are doing and what you are trying to do. That in itself can help you figure some things out. As is said, if you can't verbalize it, you don't understand it. So trying to put things into words can show you where you are deficient, and can also make you realize what you are actually doing and not doing. All of this leads to being able to have a PLAN for the next time in order to go faster. I'm a believer in just trying to go faster doesn't teach you much. Having a plan is what allows you to safely improve.
Hope that all makes sense and helps.
