Before explaining on how to become AD carry I will first explain on how to ensure you will get your AD carry.
First thing you say in champ selection is to scream:
"adc", "AD bot", "ad or feed".(pick any)
Secondly if someone asks you why you want it or when "you iz gud ad curry" answer:
"I like icecream does that count as an answer?"
"I am far more handsome thus I deserve the ad carry role!"