Hey Maloco87,
I'd start with a very basic HUD - VPP/PRF/3bet/WTSD/Hands.
You just want to make sure you spend more time watching the game than checking your HUD

Gameflow > HUD, notes > HUD ...
About the notes ...I think that it's ok to have something like:
1) some basic things like - AQs 4bet shove 100bb deep
2) questions you want to find out about the player - cbet 1/2 fold against raise 3/3 (exploitable?)
3) some lines he played esp you want to figure out his tendencies on the turn. Does he check back with showdown value or just bet?
"NL4, 24.7, CO vs BTN, A9o
A84r82 - called cbet 1/2, chb, x/b (thin)
4) How do you want to exploit this guy? (you basically put together all notes you have) for instance.
Exploit his cbet 1/2 - giveup range.
Turning sd value otr against thin value bets on Axxxx boards after checked ott.
5) if you know he's somehow good player and takes notes you can write here anything important he knows about you ...
Good luck sir!
Cya ^^