You should be reraising 2-3x what's in the pot with aces. When you raise and are reraised, you want to throw down the hammer and your 3-bet should be at least 3x the reraise. Few people will reraise and fold, so get their money before the flop.

Another strategy to consider is the all-in initial raise with AA. This works well when you are at a table where you have seen a few preflop all-ins called and when you are in late position or the blinds with a lot of limpers. Also when there is an EP raise and several cold callers. Even if it is folded around after you push 2/3 of the time, the times you are called are gold. A critical thing in getting the most out of AA in NL is knowing how to get the most money possible in the pot preflop, because you know you have everyone dominated preflop.

There are 2 ideal situations for AA in NL. The first is getting it all in preflop, and the second is flopping the nut set or a flop of 3 of the same card (the best flop for AA).