I think you have to get it in with Kings, even in a scenario where you identify he has a strong hand, all but one of those strong hands (i.e. AA) you are ahead of.
With KK's and QQ's i normally just raise 2.5x if bet is currently limp or small.
I mainly play MTT's , so i don't know if this is the correct play for cash though.
sometimes on the bubble, you can fold KK, there's nothing like that. There are cases when players fold AA preflop and were right. Much depends on the situation and the game itself.