Part 1: Creating the thread:

To create an unofficial clan you must create a thread in Clan Discussion. The title must be formatted as follows: (Clan Tag) Clan Name. Try to keep your tag short and keep in mind that if an official clan already has your name or your tag you'll be asked to change it. Every clan's first post must be fully complete within 7 days. A complete first post has:

A clan story or description.
Aims, goals, and inner-clan guidelines
If you have a clan bank you must state all users that have access to the account and also state who can access the account as well as the account's name. If you don't have a bank then you may ignore this rule.

Any other parts of your post are optional, but keep in mind that how you present yourself will affect how you are judged. Good clan DSCs do more than just the minimum and present the clan in a clear and concise fashion.