Write a journal detailing what subcultures you belong to. You can focus on 1 and write about it in detail [what, when, how, etc.] or write about a few more with less detail.
For example, I might write about being a WoW gamer, which can be quite different from other gamers. I could also write about living with a disability [did you know disability is its own sub-culture?].
As a reminder: 1 single-spaced page, Times New Roman 12 pt. font.