Many clans in the world do not advertise their presence to others. These include, but are not limited to: clans for channelers outside the Aes Sedai, clans for male channelers, many thief and bandit clans, and other clans who, for whatever reason, wish to preserve their anonymity. Although each clan is unique, there are some general guidelines which apply to most, if not all secret clans.
First, they do not accept casual applicants. Characters must first demonstrate through role-play over a period of time that they are in fact the type of character the clan would like to include. Second, they guard their secrets carefully. New members may not even know many of the other members of the clan, that information being reserved only for the higher ranks (the clan masters who actually administer the clan).
Some clans do not even accept applications, they invite characters they feel are worthy of joining their group. Careful consideration must be given to such offers, as some clans have been known to not take refusals too kindly.