It depends in what situation, but I would never fold AA, unless it was a satelitte and I was already 99% sure I would got a ticket if I fold. If it is early in a full table I would bet or raise if someone have made a bet before you. If it is late in a turbo tournament and the blinds are high, and someone bets, and you think he most likely would fold to a raise. Then you could flat call, and hope he cbet bluffs on the flop, so that you get more value. Most of the times I would make a big raise, but sometimes I like to play it tricky and try with the hand.