I tend to note strange actions that I would either be wary of or could misread as weakness. These are usually limp, min-raise or open push hands.
Examples would be: "Open push AA mid position, SNG, lvl1", "Limp AK on button late MTT", "min raise 89o UTG+1, SNG 50/100".
Other notes might include if the opponent stacks off with top pair, calls loosley or tightley esp. in bubble situations, chases draws without the right price and if he slowplays hands or not.
Revenge notes are also fun ...
