A lot depends on...well, a lot. How deep in a tourney, stack sizes, etc.
But generally...I try to open with about a 5X BB raise. The idea with AA is to get ONE caller. More callers gives you more of a chance of getting sucked out, so limping is defintely not a good idea. If you get re-raised, great...push all in and either they fold or call you with a lesser hand.