Depend the read about other players and if have any moves before you, but normally I raise 2x-3.5x BBs + 1 BB x limpers. In flop if just one call me, I c-bet most of the time even if I am not in position and even if I have not hit anything that improves my hand. In turn I think if my hand is good or not and I'll evaluate if it's worth bet or check.
Depends on the usual factors - blind level, stack sizes, position, reads, action to me. But to generalise I'm usually raising 3-4BB if it's unopened, calling or re-raising if not. However, the right actions from the right players before me (i.e 3 and 4 bets from tight players) could make me fold AK.
There is no simple answer due to all of the variables, but AK should be a raise or reraise a vast majority of the time. About the only time it isn't for me is if a tight player has already 3 bet before me, in which case I'll likely flat if it isn't too much of my stack. However if the original raiser is fairly short stacked and I think there is a good chance they will shove, I might fold. Also if I am at/near the bubble in a satellite I might fold depending on stack sizes.