Go by your interests. Like there are probably clubs or groups you could join to meet others who like chess or anime or golf. Also you can always just go by how people dress. Teenagers who don't play sports often form their identities and thus their bonds based on music, and you usually tell what kind of music a teenager listens to by how they dress.
BTW, identifying yourself strongly with some kind of group is part of being a teenager. That is, even the nonconformists are conforming. It's a normal stage - little kids care desperately what your parents think, teens care desperately about their peers think, eventually some of us learn not to care too much what anyone thinks (except maybe the boss). So don't go around scoffing at conformists because older people will just laugh at you.
