I make quick notes of unusual characteristics or hands if they come up. These would be things like limping premium hands (high pairs) into pots with lots of players... doggedly chasing really longshot draws (like 4-outers) even with the worst imaginable pot odds... chronic slowplayers... chronic check-raisers... chronic bluffers... etc. For most people my notes are just one line, like this:

- Big fish, flush-chaser, don't try to bluff
- Calls too much but will fold to aggression on later streets
- Solid player, respect his raises