It is so dependent on the situation and chip stacks. I might just call and look to reraise the turn again to see if he is really interested. You really can't worry about sets much. Sometimes you are just going to lose.
Depending on how big the pot is and how big the raise is i would either call or fold. Generally if the pair is higher than the third card it is more likely that they have trips. If the third card is higher than the pair than players will often raise with their two pair.