Keep your notes brief,stick to basics like -
tight
loose
aggressive
passive/weak
add to them any tendencies you pick up on , as you are in your early part of your poker life, try not to clutter to much info in,with experience you will begin to digest more..So to begin i"d suggest noting basic tendencies like -
Over plays of top pair
Over plays of a over pair
How they play 2 pair plus - then add - do they check raise,lead out strong,re-raise sets on the flop for example etc etc
How do they play draws - lead or call - bet strong or do they baby bet for example
Do they call and fold a lot to betting on certain streets
Watch for continuation bets OOP on the flop - do they continue from 4th street
Watch shown hands and try to build a picture of your opponents - do they show down only strong hands or are they weak holdings [with experience you will get a feel for your opponents and there style of play]
hopefully this will help you get started...In time and with playing experience you will know yourself how much info you need to note,just play and review your histories every now and then is a good start mayfair and practice your hand reading all the time in or out of a hand,always concentrate on what your opponents are doing.
here is a earlier post that may help you [but again dont try to digest everything all at once,bit by bit master one part then move on to other areas of your game]
http://www.apat.com/forum/index.php?topic=1936.msg31539#msg31539