Ok here we go:

There are 2 ways to start xgl ,

  • If you want to start xgl when gdm starts , follow the the “normal” howto! The downside of this way to start xgl is that you can not start a normal gnome session (non xgl) , atleast not trough gdm.
  • If you still want to be able to start a normal gnome session , folow the “second” howto! That way you can choose between an xgl gnome session or a normal gnome session. The big plus is that if something is wrong with xgl , you still hava a desktop available.
  • If you used previous howtos , be sure to remove or modify all the changes you have made!

[ From Beryl – Forums & Community ]