i hav no idea probaly try to talk to him as if he were a normal person (but don't worry he is lebih than just a normal person He like the hottest person on this earth) because it would be crepy if I started screaming. lol
If i honestly met justin Bieber i would have a huggeee smile on my face and i would be excited(: i mean i wouldn't be all over him becuz i know most famous people doesn't like that(: lol