The guild changes are now finally in! Most eligible guilds have been transferred into the game, and BioWare have chosen their servers. Be sure you check your guild home page or the Guild HQ for your guilds server name, before you get into the game.
Guild HQ: http://www.swtor.com/guilds
Here is BioWare article on the subject, and guide: http://www.swtor.com/blog/guild-deployment-details