We must ask the question: why are we in multiway?
Make sure that you open AA like any other hand in your pre-flop range. Never ever limp this unless it's a final table short-stack trap. Now, opening strong pre is certainly no guarantee that we will get isolation or even thin the herd but if we open AA properly we shouldn't be multi too often unless maybe it's a freeroll.
Post-flop we are basically always c-betting for value except on the grossest ugliest boards. Other than that, the only time that I might check this is if I actually flopped a set because it blocks most made value (there is only 1 A left to hit top pair) but if the board is wet, no free draws so bet. Also, even in say a 4-way SOMEONE will probably be dumb enough to call you without an A for top pair, so it's probably never a mistake to bet.