There is no global chat. Thankfully, from my perspective. There is zone chat which is shout (/shout or /sh). It isn't used much in the lower level areas but if you can get to Mor Dhona it is constantly in use.
The area based talking options are:
  • /say - a small area around you
  • /yell - a large area around you
  • /shout - the entire zone
But mostly people talk in group specific channels. These are:
  • /party - the adventuring party you are in
  • /fc - the free company you are in
  • /l1-8 - you can belong to up to 8 linkshells which are player created chat channels. You must be invited to one to join.
You can, as you have done, post here on the forums and ask for server specific groups.