try playing 1 table at a time. Play enough at given stakes/games/sites to have a general notion of what a typical player does. Take notes when someone does something "out of the ordinary".

but you need to reverse your question: Don't try to put people in categories and try to figure out what those categories do. Try to figure out what people are DOING, and use their actions to to put them in categories. It's self defining. I.e,. someone who doesn't bet or raise alot is "passive". But you don't know that they are passive until you OBSERVE them "not raising". Once you have made the observation - you can predict their future behavior.