well that depends a lot on what kind of players you are facing. how is the dynamic of the table?
then position comes in play. are you utg? middle position? cut-off? button? SB or BB?
what actions have the players before you taken? what kind of players are they? (it's easier to put the tight players on a certain range. it's much more tougher to put the loose ones on a range)
is it smarter to try and take down the pot pre flop by going all in? (or at least in this manner, by going all in pre flop, you isolate and get calls from smaller pairs or some short stacks who call with suited connectors or ATs etc.)
if you play AA or KK out of position anything can happen, as a player hits the flop 1 of 3 times (i can't remember where i read this though, maybe someone has other info on this subject).
as an example: i'm BB with KK. UTG limps in. everyone folds, including SB. i raise 4 bb. he calls. flop comes 9 3 5 rainbow. i c-bet half the pot. he calls. i continue to bet. he calls. i go all in, he calls and shows 33. plus the 3 on the board=trips. and i'm like: how come i didn't see this coming?
but you shouldn't be very concerned, your time will come
+ AA kicks ass 85% of the time and KK around 80% . then again, AA vs KK is roughly 80-20. think about it.