there are many ways to play aces - even a few reasons to fold them preflop - but you are too inexperienced for those right now
my theory- unless there is action before you bet - is that you should ALWAYS be raising the same amount with every hand that you are raising with...this way your opponents cant get a read on how strong your hand is - BECAUSE if they know you have aces they will probably fold - I like 3x the big blind. Poofy has a good thought though with people acting before you do - if you get a lot of callers before you act (3 or more) then your raise should be slightly higher to weed out the riff-raff