For the Haudenosaunee, you are either born into the clan or adopted. In the first instance, your mother's clan is your clan, as we are matrilineal. Also, no two people of the same clan can marry, and this is highly stressed across the Longhouse Nations. For example, every person in a Wolf Clan, no matter what Nation they belong to within the Haudenosaunee, are considered almost like family to each other. Myself, I belong to the Coyote Wolf (Little Wolf) Clan of the Mohawk Nation, and presume I meet someone of the opposite gender from the Mohawk Timber or Grey Wolf Clans, or any Wolf Clan from the other member Nations. Any notion of a quick tango or prolonged romantic interest would be considered quite literally as incest. (There are the rare cases this has happen, however. Not to mention what Urbanlamb would do to me.)
As for clan identity, our people would display their relevant animal symbol on their clothing and the walls of the longhouse. This practice continues even today, with the symbol displayed in their homes and used as part of their signature.
Mohawk: Wolf, Bear and Turtle
Oneida: Wolf, Bear and Turtle
Onondaga: Wolf, Bear, Turtle, Deer, Eel, Hawk, Beaver, Heron and Snipe
Cayuga: Wolf, Bear, Turtle, Heron and Snipe
Seneca: Wolf, Bear, Turtle, Deer, Hawk, Beaver, Heron and Snipe
Tuscarora: Wolf, Bear, Turtle, Deer, Eel, Beaver and Snipe
This just scratches part of our societal makeup, and if you're interested, I will try to put together a synopsis outlining our laws and traditions.