You want to take every advantage you can. While you don't get to see people, you can use a program like PokerTracker to get more information on them. You can see exactly how often they've been playing hands, how often they bet after the flop, etc. The HUD will also show you players cards when they go to showdown yet muck. (These hands are show in the hand history, but the HUD digs them out and displays them for you). That way you can see what they were calling down with.
The best way to read people online is to see how they play what they do with what hands in what positions. Seeing their stats in PokerTracker can put you in the ballpark about what sort of hands they're playing.
you were looking for are called "click tells." They are less accurate. It's basically looking for how long it takes people to respond. For example, if you raise, then someone waits a long long time to respond, then he shoves, he usually has a very big hand. But he could also be having connection issues, or talking on the phone, or distracted at another table (some people play 20 tables at a time).