How to change the display manager from GDM to SLIM?

[Kennet R. Iversen]

I have tried to get slim to start as my login manager instead of gdm, 
but everything I have tried so far has not worked.

I have installed slim via yum and then tried the following approaches:

First I tried to put the following line in /etc/X11/default-display-manager
    /usr/bin/slim

That did not work. Then I tried to put this line in /etc/inittab:
    x:5:respawn:/usr/bin/slim >& /dev/null

This did not work. I then tried to put this line in /etc/sysconfig/desktop
    DISPLAYMANAGER="SLIM"
and then added these to lines in /etc/X11/prefdm just after the 
GNOME/gdm part:
    elif [ "$DISPLAYMANAGER" = SLIM ]; then
        preferred=/usr/bin/slim

This did not work either. I have not been able to find a solution that 
works. So, how do I change the default display manager from GDM to SLIM?

Any suggestions are welcome
Kennet