re: How do you know your opponets exploit you?
If you suspect someone is exploiting you then it's highly like you are beig exploited.
You know you are being exploited:
1. if every or most times you raise someone re raises to isolate the so it's just you and them in the pot (usually the same 1 or 2 people, maybe even 3 if you are on a v god table)
2. if every time you raise and end up going to showdown a good player tables something ridiculous like J5 suited for top or middle pair, they did not call you for the flush, they called you to outplay you post flop, the if the flush came then hey... but that wasn't why they called your raise with J5
3. if someone seems to have your number every time and you are having to fold before showdown most of the time and they seem to be folding the one time that you have a hand. (this type of exploitation means they have a solid tell on you, the best thing you can do is try to figure out what that tell is, but that is a difficult thing to do unless you have a friend that can honestly tell you if you have tells at the table, the second best thing is to find one position that you will sit in and 'robotize' yourself, have very limited movements, put your chips in the same way every time, take roughly the same time each time, find a spot you will stare at every time you are in a hand, be in complete control of every movement you make, (this is for live play, I'm not much of an online player but some of this should be helpful online too
For online you also want to watch your betting patterns (including time taken) don't play your draws the same way you play your TPTK.
Try to always have position or control of the hand when against someone you suspect is exploiting you, Be a bit mysterious, check raise someone you feel might be exploiting you when you have nothing 9+ outs, but don't give them the stare down or alert them that you are aware of them exploiting you, allow them to win insignificant pots, and try t take the ones that matter.
If you feel you can't outplay them, just be real with yourself, it'll save you money and avoid getting in pots with them where you don't feel you are ahead.