Why am i so anti-social at times around new people? How do i adapt to new things?

Iv'e known them for about 5-6 months and most of them i start to talk to but some of them i dnt talk to unless they say something to me. I guess its because im a pisces and im very shy. But i also at times jus dnt like people because they be so childish. lol Sometimes i jus play phony lil games actin like i dnt wana talk and i jus ignore. But how do i adapt to new things??