It is not enough to simply classify players as "good" or "bad" because we don't have any tendencies described to exploit or defend against.
That's like men asking "what do women want?" pretty hard to answer....need a lot more specifics. Are we talking about trying to date college girls, are we talking about buying a birthday present for your mom, or are we talking about getting a promotion from your female boss? The more details you have the easier it is to come up with a successful plan.
Sounds like you need to work on developing your player reads. So do I, it is a skill I am constantly trying to improve. I'll tell you what I look for when I sit at a new table:
#1 just start with observing the 2 players to your left and the 1 player to your right. These are the people you are most likely to end up in pots with. As you get a handle on those players, you can add 1 more player to your left, and then a little later 1 more player to your right and so on.
#2 initially look for loose vs tight. To me, this means a % of preflop hands played. So if a player plays less than 1 hand per orbit he is fairly tight. if he plays less than 1 hand per 2 orbits he is really tight. if he plays 1 hand per orbit he is maybe average. if he plays 2 hands per orbit he is on the loose side. if anyone plays 3 hands per orbit they are definitely pretty loose. Don't count it when they just check their BB or complete from the SB. Do count the hand if they call a raise from the blinds.
#2 Next look for passive vs. aggressive. are they usually limping, calling or folding? or are they usually raising or re-raising?
#3 Next look for position. do they vary their play based on position? i.e. are they tight in early position and open up in late position. Do they call raises out of position?
#4 Do they defend their blinds? How do they defend their blinds? Do they call and then check fold the flop if they miss (loose passive)? or do they raise from the blinds (aggressive)? or do they call preflop and then lead on the flop (known as a Stop n Go)
That is enough things to look at for now. it will keep you busy for many many hours of practice.
Eventually you should have a model of the player "Tight Aggressive Position player" "Loose passive calling station" "Loose Aggressive who bluffs a lot"
When you have a fairly reliable model of the player, then you can start developing counter strategies. For instance the tactics you would use against a Loose Passive player are very different than the tactics you would use against a Loose aggressive player.
In general, the best strategy is to do the opposite of their observed tendency. So if they are loose, tighten up against them if they are tight loosen up against them. if they are passive, bet at them. if they are aggressive, let them do the betting for you. There are exceptions to the "do the opposite" guideline but it is a decent place to start.
Hope this helps!