I note anything I think may be noteworthy. If I see a player limp with AA UTG I will note it. If I see that he limps in
LP with a suited king i note that.
Probobly the biggest advice for taking notes I have is for when playing Razz. I will quickly type in all of the exposed cards in order so i know what was out. I jsut type them really quick into the chat box and erase them and do it again at the begining of every hand. I guess thats my little Razz trick of the day.