Every year, the hottest A-listers flock to New York's Metropolitan Museum for the annual Met Ball. It's a super-fashionable affair (hosted by none other than Anna Wintour this year, natch) so let past guests Blake Lively, Cara Delevingne and Alexa Chung give you a whirlwind education in how to pose like you're on a red carpet. Vogue for us, darlings!