There have been a lot of good comments posted on AK. The biggest thing to remember is that you are playing a drawing hand not a made hand. I don't want to be redundant but it is a hand that can be overplayed as mentioned. By reading this I also see how it is underplayed by a lot of people. Yes it is behind dueces especially when we miss the flop but you still have a draw to two big cards and chances are your opponent with dueces is shaking in his boots. A continuation bet is almost a must with AK because unless they flopped a monster your drawing to the best hand. Now I'm not saying you have to bet the pot, you really shouldn't being betting the pot anyway on the flop so that your keeping it small. Don't ever let yourself or your opponent get pot committed until you know that you have the best of it. I feel for those players that say they always lose with AK. Because to be successful at hold’em you have to win with an AK and you have to win when you are against an AK. AK is a hand that you raise with from any position. And if you have been watching your opponents you might even re-raise with it against most of them. But I do not suggest that you ever re-raise with this hand from the little blind or the big blind (unless it came from a late position raiser who appears to be stealing the blinds) because you will have to act first from the flop on, which puts you out of position. AK is a positional hand! But you should always be putting your opponents on a range of hands from the moment you get involved with them. If the flop does not appear to have made them overly strong try making a bet; if nothing else they're going to stop and think and you remain in control of the hand. This is not a bluff it is a semi-bluff which conceals your hand if an ace or a king does come off, not to mention your ace high may be the best hand. If you get played back at re-evaluate and if you don't like the feel of the situation muck em. Where people misplay AK it is because they either get married to it, or they play it weak and don't steal when they could've stolen and let people catch up and pass 'em.
To address an earlier post about being a coin flip to all under-pairs that is not entirely true. It is a 70-30 dog to kings but a coin flip to all other under-pairs. To find the reason for that just calculate the odds. Take the number of outs you have times the number of cards to come times two. So in the case of AK vs QQ we have essentially 6 outs with 5 cards to come. 6 * 5 = 30(2) = 60%. But this 60% has to be discounted because our opponent could hit a Q which would crack our pair with a three of a kind. Basically that is how the two over cards work against the underpair but you ca use this formula and should use this formula throughout the game to calculate odds. For instance lets say you flop 4 to a flush and your opponent bets into a pot of $200 a bet of $50. Well the odds of hitting a flush on the turn are your 9 remaining, lets say hearts, times the one card to come on the turn times two. So basically 20% or 5 to 1 (9 * 1) = 9(2) = 18. Meaning 1 out of times you will hit your heart flush on the turn; assuming that no other hearts have been dealt out of the deck. But we don't have any information to make us assume otherwise. Now your are only getting 4 to 1 on your money so should you make the call? Well most of the time. If you believe that your opponent is liable to pay you off when you hit you should call all the time. You may want to reraise in this spot to disguise your draw, pickup fold equity and perhaps earn a free card on 4th street if your out doesn't come. Hopefully this helps answers the questions about the 2 - 4 rule and if not let me knom and I will try to post some more examples.