first off, make sure to read all the stickies in the appropriate forum. then, when you face 'big raises when you have TPTK' save the hand history and post it here with your reads of the villian (i highly recommend PokerTracker if you can spare the money). nobody can give general advice like always fold TPTK to a raise or never fold it etc... but if we see the specific hand we can give specific advice.

Also, a big thing that you absolutely MUST know if you are just starting out in cash is Bankroll Management. 20-25 buyins is a necessity. if you want the reasoning, click on the link. good luck.