It depends on the flop texture. If it's a generally dry, uncoordinated flop, I like to c-bet 3/4 of the pot.
Of course, this also depends on the villain or villains.
However, if it's a very wet board, I normally just check, assuming I'm first to act. However I always c-bet the flop if I'm last to act.
But, honestly speaking, there are just too many factors that I take into play. The thing about AK is that even though it's a strong hand, it's a drawing hand which you need to know when to throw away when things seem to be going horribly wrong.