Because I only play NL trnys, I will stick to that. AA can be played many ways preflop, but it all depends on the situation. In the early levels of a trny the blinds are so low that raising 2 to 3 BBs wont usually push out weaker hands, so if you raise, raise big. The problem with this is raising big early in a trny will only usually win you the blinds, which isnt much early on. Remember, though, better to win a small pot than lose a big one. So early on, I'll try to limp from any position if I don't have a raiser in front of me. If I do have a raiser, I'll reraise and try to isolate him HU. If his raise is big enough that I wouldnt mind him folding, I'll push all in and race him if he calls.
The most important thing to remember with AA is that, while it is the best starting hand, it may not be the best hand after the flop. Anytime I limp with AA, I do it hoping for a raise, preflop. If I don't get one, then I'm forced to play the flop more conservative. Do not be afraid to lay them down. If you find yourself not able to lay them down post flop, then raise preflop every time you have them, from any position, so your not matched up against weaker hands. If you've never folded AA post flop, I suggest you work on your discipline. One of the most important actions in poker is folding, and if you can't lay down monster starting hands post flop, i.e. AA, KK, QQ, etc., then you'll never reach your full potential as a poker player.