Creating a guild requires nothing except a leader and the ability to read and write. It\'s possible to create a guild in-game but that doesn\'t make it official.
If you want people to join, though, you might want to consider setting up a website and some forums.
Make sure you thoroughly think out the guild first. Have a clear goal, what strives the guild to exist. Have different ranks within the guild. And many guilds also have histories, which are good as long as they conincide with the world of Planeshift. (Yes the CV\'s is coming...soon-ish-ly...)
If you want some good examples, just browse through the other guilds website and forums.
Hope that helps.