I wonder how to use XQuartz to communicate with the Centos server through a local graphical user interface on my Mac? I did the following steps so far, and the result so far is just connect to the server through terminal.
Installed gdm on the server.
Switched run level to 5.
Installed XQuartz on my Mac OS 10.8.
On Terminal: ssh X root.website.com.
After doing what @onik suggested (using the xterm instead of terminal, created a new user other than root, and entered the command gnome-session), I get the following warnings before xterm halts: