Well... have you seen the blue banner above my avy saying "Nayru Clan"? Well, I am a member of the Nayru Clan. You may have also noticed people with banners saying "Din Clan" and "Farore Clan". The one you get into depends on how you answer to a personality test. Anyway, read the
Clan FAQ and once you have been a member for a month and have at least 50 posts, you can ask to get a test from the approved mods (I suggest Awkin). Then they send you the test, then you answer it, then you send it in, then you get in a clan! Clans are fun. They are basicly spammy places where you can just hang out and talk about nothing in particular. You should make a point of getting in one.