When I got tired of using the standard XFCE window manager, xfwm, I simply installed openbox and selected "XFCE/Openbox" session in the GDM login screen. This was very convenient because I didn't want the plain Openbox session in which there are no network-manager, no panels, nothing.
Now I have installed awesome: I really like the idea of tiling window managers. But after I launched it, everything went wrong. Absence of XFCE panels isn't anything bad, but subpixel-aliased fonts were somehow turned on, and that was really awful.
I tried to login in XFCE, kill openbox/xfwm and start awesome, but that didn't worked: xfce4-session keeps restarting it's predefined WM, and killing it kills the whole X session too. And I didn't found the configuration for a dropdown list in GDM either.
How can I start XFCE session with awesome as a WM?