I usually re-raise a raise with AK to narrow the field to a possible heads-up. If the re-raise is made by a short stack, I will re-raise for most of their chips. This tells the rest of the table that I have a hand that I'm willing to flip over pre-flop.

I'n a ring game of even stacks, this is not an all-in call or push pre-flop. In a tournee, pros often say that ones tournament will be determined by whether or not they win or lose with AK.