Aside from the things already mentioned by others, I also find that one of the things to look for online is whether or not the person exibits a pattern as far as how many streets they will pay to see, i often find i can categorize players in this way as we.. ie player A... tendency to see flops, but often or always folds post flop, player B... will see most hands to the turn... keep in mind that in order to gain this kind of info on a player and put it into a pattern you cannot be playing weak after the flop, they have to see a price for every card. (not difficult for me since i like to make em pay for every street if i stay in the hand)