These players are the most dangerous in that they may have tendencies of being solid and weak, many of them in poker learning stages that may well be improving. I find the reason why these online poker players are stuck in this zone is that they can’t let go of draws, even when pot odds justify an obvious fold. The course of action here is basically straight up, unless you have some other indication of their play. If you have them on an obvious draw, bet solid. If the river is a brick add one small bet to cap it off, and hope for a re-raise. In game play, they are the ones to watch most in order to help build an identity.
0% to 20% - Fish: Don’t bluff, don’t bluff, and for God sakes, don’t bluff. These are the players who are most often asked – “How did you call with that?” They are the lowest grade opponents for a reason, but can double up ON YOU if you don’t play straight up against them. However, that makes them the most susceptible to being trapped and/or slow played. And that’s what you want to do while avoid being drawn out on an ugly gut shot straight. If you want them out of the hand, all-in is your only play, but make sure you are way ahead. If not, calling/checking down, and folding to a huge river bet is safer. These players will see so many hands and raises that you are sure to get a better shot at them later - if they happen to survive.
How many games have they played? The more they have played (100+) the more that category is true to their fundamental playing style. If your opponent has a 62% win rate but has only played 13 games, you are essentially playing blind – the win rate is a non-factor, save for representing a streak.
What buy-in are they playing compared to what they usually play? Someone could be on a bad losing streak at the $50 buy in, and finds himself trying to bankroll at the $10 buy ins. They may tend to be more impatient and inclined to tilt. On the other hand, moving up a level or two usually means the player is going to be much tighter.
Conflicting styles. If you discover a pro-rated player in a lot of weak hands, and playing carelessly, you may be seated with the spouse/friend of the account holder. I often come across this and pay close attention to that player so that I can override the category myself.