Here's my ~/.xsession file, to explain how you can setup X to start certain wm's and apps.
Code:
#!/bin/bash
xhost +localhost
xscreensaver &
if [ -e ~/.profile ]; then source ~/.profile; fi
if [ -e ~/.bash_profile ]; then source ~/.bash_profile; fi
if [ -d ~/.app-defaults ]; then export XAPPLRESDIR=~/.app-defaults; fi
if [ -e ~/.XDefaults ]; then source ~/.Xdefaults; fi
if [ -x ~/bin/fontinstall ]; then ~/bin/fontinstall; fi
if [ -x ~/bin/alsavol ]; then ~/bin/alsavol restore; fi
## blackbox ##
#bbkeys -w -m &
#bbpager &
#gkrellm -w &
#exec blackbox
## other wm's ##
#exec enlightenment
#exec fvwm2
#exec fluxbox
#exec sawfish
#exec gnome-session
## kde ##
exec startkde