Before I take any notes on players I make a subtitle in the note box of what game/stakes they were playing.

For example:

"$25nl full ring"

"$5 SNG (18)" (where the number in brackets is the number of entrants)

Then under where I saw this player, I add notes using bullet points below. If I have a regular who is playing multiple games/stakes I may have several different headings. Under each I will note interesting things they do that don't really add up with their stats, or perhaps something that they do which stats will tend to ignore. For example triple barrell A9842 with JT allin 100bb/overbet shove river with nuts/call down 2nd pair vs me on K9247.

Not saying these notes are that great, they're the only examples I could think of at the moment. I kinda suck at note taking, but I think my overall organization is alright. Note taking is something I'm aiming to improve at the moment...I just started keeping track of the stakes/game of the players since I have noticed some tend to jump around like me.