Badly Played AK Advice Please

I have been playing only about 12 months and am a complete novice !!. Last night I made it almost to the last table and got busted out eleventh.

5 players on my table everyone folds to me on the button. I have A [img]/images/graemlins/club.gif[/img] K [img]/images/graemlins/spade.gif[/img] and raise two similar stacked (NB we are all good size stacks)but I get my raise wrong and do not put enough pressure on the BB. (1800 in pot I raise it to 2400 total he calls SB fold BB calls 1200) flop comes KT( [img]/images/graemlins/heart.gif[/img]4 [img]/images/graemlins/club.gif[/img] BB raised 3000 I come over the top and put him all in. He calls and makes a flush with his 86 [img]/images/graemlins/heart.gif[/img] on the river.

Notwithstanding I should have raised more on the button how could I have played the flop situation better and should I have just gone all in preflop regardless. The way the guy was playing a flat call preflop would have induced an all in from the BB.