One of the best things about this game is the team work that is needed to succeed, and to get best accomplish that you need good communication with the players all around you.
The best way to do this within an outfit is use a programme such as TeamSpeak, however you will often find times when you need to quickly communicate with random players around you.

Fastest communication - Voice Macro Tree
Standard Chat - / (Slash) Commands
Add spice to your chat - Colour Commands