Pre-flop it is simple, call, maybe I can fold, if he have more chips, and it is affecting the money, like in bubble in a medium, high stake tourney, before the FT, and I have enough stack to wait for better situation, but it happens rarely.
The flop situation depends on the board, of course with K or A down, without my Q or K hard to call, but it depends on the opponent, too. Also hard when a straight option is down, like 789 or the doubled cards 1010x or JJx. In these cases there are plenty things what makes me decide.