What are your observations of the player? Is he highly active and playing tricky after the flop? All you need is to see a few involved hand histories where he went to showdown. Then you replay the hand knowing how he played top-pair, a set, a draw, etc. and go through his thought process. Did he slowplay the flop, then spring the trap on the turn against other players? Then use this in conjunction with your read and how much strength you've
represented, and think if the story checks out.
Once you have a 10-15 such hands, you can start playing better to extract value and losing less.
It's really hard to develop reads on strangers. The more hands he does this with that you beat - you don't beat any of the set combinations, are there two pair combinations that make sense? If he only ever does this with made hands, on K65, you can let go of a pair because his turn check-raising range has you beat. If he does this with draws, and you hold an overpair and there are possible weaker overpairs (say you have KK on 238), you can be more inclined to reraise, call, shove. If you call, and the turn and river blanks out, be prepared to call down. Sometimes you'll be wrong, but what's important is that the odds are more in your favor the wider his range is.
I usually try to play smaller pots with strangers until I get them. Unless you're playing on a mega-site like PokerStars
, you will eventually find regulars and as you understand them better you'll get better at taking their money.