How should a teenage girl behave or carry out herself when in a big crowd of other teenagers who include both girls and boys?

Yes. Be yourself. You will find that if you mingle and converse with individuals in the group as your own person, with your own ideas you will be liked for who you are.

The wonderful thing about being liked for who you are is that you never have to remember who you were pretending to be. You will find your friendships to be true and real. Easy to maintain because you are not consuming your mind being fake.

You will find that the people that like you, do things you like for you

Don't try and be something you not and be yourself and be confident. Also for the comment^ I am like that but I just try to be confident and just go for it trust me it works because I'm not really like that any more only sometime ...(if theres a really hot boy :P)