[ls@arch ~]$ uname -a
Linux arch 3.1.0-4-ARCH #1 SMP PREEMPT Mon Nov 7 23:21:44 CET 2011 i686 Intel(R) Core(TM)2 Duo CPU E7500 @ 2.93GHz GenuineIntel GNU/Linux

================================================================================

With XDM (inittab):

[ls@arch ~]$ ck-list-sessions
Session8:
	unix-user = '1000'
	realname = 'Lampslave'
	seat = 'Seat1'
	session-type = ''
	active = TRUE
	x11-display = ':0'
	x11-display-device = '/dev/tty8'
	display-device = ''
	remote-host-name = ''
	is-local = TRUE
	on-since = '2011-11-11T18:27:10.707415Z'
	login-session-id = ''

================================================================================

With XDM (inittab):

[ls@arch ~]$ cat .xinitrc 
#!/bin/sh
#
# ~/.xinitrc
#
# Executed by startx (run your window manager from here)

if [ -d /etc/X11/xinit/xinitrc.d ]; then
  for f in /etc/X11/xinit/xinitrc.d/*; do
    [ -x "$f" ] && . "$f"
  done
  unset f
fi

# exec gnome-session
# exec startkde
# exec startxfce4
# ...or the Window Manager of your choice
export GTK2_RC_FILES="$HOME/.gtkrc-2.0"
exec startxfce4


Or with Slim (daemon):

[ls@arch ~]$ cat .xinitrc 
#!/bin/sh
#
# ~/.xinitrc
#
# Executed by startx (run your window manager from here)

if [ -d /etc/X11/xinit/xinitrc.d ]; then
  for f in /etc/X11/xinit/xinitrc.d/*; do
    [ -x "$f" ] && . "$f"
  done
  unset f
fi

# exec gnome-session
# exec startkde
# exec startxfce4
# ...or the Window Manager of your choice
export GTK2_RC_FILES="$HOME/.gtkrc-2.0"
exec ck-launch-session dbus-launch startxfce4