Note Taking in Live Games and Tournaments

[LockLow34]

Who here keeps notes on players they play against in live games and tournaments? What information do you keep in your notes? How do you organize them? Do you have a notebook with you to refer to and write in during your play?

I saw in Harrington's books a passing reference to note taking, and also saw Greg Raymer taking notes during the 2004ME (the hand where Matusow was taunting him). I'm just wondering what info is tracked and kept and what is not.