Most importantly, the cards I am holding have no bearing on how I am coming into the pot. You were asking about AA or KK in early position, but I play them the same as I would play JTo, 44, 96s or AKo. My position dictates if a hand is playable, but once I decide to play it, I'm playing it the same as any other hand from that position.
Every time I arrive at a new table, my first order of business is generally to look for the aggressive players. I want to quickly find out who likes to raise preflop, especially those that come in for a raise with limpers in front of them. Based on this, I can generally determine which positions are likely to be favorable for a raise after I come into the pot, and those positions are the ones which I will limp with any cards that I choose to play. I can then either re-raise or fold, depending on the cards that I am holding.
For example, if there are two aggresive pre-flop raisers at my table, then I will only open-limp in the positions where I am acting before them. If they have already passed, I will raise if I'm coming in, and if they limp, I will pass unless I have a hand that can stand a reraise. (Of course it's possible that they are limping with a multi-way hand, but it's far more likely that the limp is a trap.)
Any time that a major change occurs (I get moved, a new player arrives at the table, or one of the aggressive players busts-out or slows-down) I re-evaluate the table positions.
Ideally, whenever I limp strong hands based on position, the table dynamics work as planned and I get raised, but sometimes it does just get called and then checked on the BB. When this happens, I play very carefully and understand that I'm probably going to want to keep the pot small unless I flop a monster.
This style of play only works if you have the discipline to fold an overpair (even AA) against significant action when the pot was unraised preflop. I find that the times that I wind up with limpers caught between the original raiser and my reraise more than make up for it.