When to throw them away

How you determine when it is time to let a decent hand (2 pair, TPGK) go on the flop or turn based on your reads of your opponent and their bets? I have gotten burned recently by being agressive with these types of hands and making people pay to play, and losing out at the showdown. What are some of the things you look for that tell you to let it go before it costs you too much?

That's a pretty general question... hard to give a good answer.

It helps to have a read on the player. Are they aggressive also? If so they would raise or re-raise with a better hand than yours (two pair vs. top pair, a straight, a set, etc.). If you bet into them a couple times and get raised a couple times, that's a good indicator that they are strong. Then you just need to read the board.

Are they more passive? Can you differentiate a passive fish from a passive tight player? If you are betting 2/3 of the pot or more and they're calling you down on multiple streets, does it seem likely they're chasing a draw, or are they smooth calling a better hand? Think about checking the river if you suspect the latter behavior. If they then bet into you, you need to read the board and draw your conclusions.