I try to make a note on one player at each table. Be warned, that bad notes are worse than no notes at all. Without a mountain of evidence, it's hard to make any relevant observations about another players style. Early on I found myself mostly taking notes on the bad players after a suckout until I realized that it was just sour grapes, and that I didn't need a note to spot a maniac in the 1st 10 minutes. I now try to avoid editorializing. I keep my notes very simple. Whenever there's a showdown I will record what each player played and from what position. Done. At FTP there is also the option of color coding another player. I use red for good or solid play, and green for bad.
More often than not I'll have a note on at least one of the other players at a table.
Call EP 10,8s
Call Min raise Button A,5
RR MP 4,4 ( reraised from middle position with 4,4)