In the shell. A nice glug of olive oil in the pan, sliced ginger and garlic, throw in the prawns. Grind some pepper over the top if you like, and/or some red pepper flakes. Remove from the heat when the prawns are pink and have curled.
Pull off the shell (suck the juices off though!). Dip the meat into whatever oil remains. Yuuuuummmmmmm.
If you must marinate, don't do so for long. Can make the end product mushy instead of nicely crisp which seems so much fresher.
And if all else fails? Send 'em over here! I'd KILL for four 25-cm prawns!!