[TexArcher]

Some very basic things that will help you get started:

I make it a point to note when I see someone repeatedly playing a weak starting hand, especially when they play garbage suited cards or they play marginal hands way out of position.

I also note whether someone consistently lets me take their blinds or whether they put up a fight.

Also if they like to see cheap flops and then consistently fold to any aggression when the flop misses them.

Also, when someone raises from late position on the flop and then takes a free card on the turn.

Also, when someone calls without correct pot odds or folds when they had correct pot odds to call even a marginal hand.

A million more, I'll try post more later on if I think about it..