sorry, i'm not much for short term goals because in 3 weeks, you won't really be able to 'transform' like you want. you might lose a 1/2" off your measurements (arms, bust, waist, thighs) but it won't really be noticable, and you'll have to do everything perfectly to even achieve that.
I would just watch what you eat, get any level of exercise, and watch the salt intake at the reception and afterwards so you don't retain water from excess sodium.