Changing default WM

[bhsx]

I've been looking everywhere and can't seem to come across a straight answer. What file do you need to edit to change default desktop environment?
Also, how would you launch a default application and make sure it stays persistent (example, knoppix-mame loads into fluxbox then immediately launches gxmame, if you exit the app, it relaunches)? This would be great for kiosk-type environments and demo CDs.

[bhsx]

For anyone looking for the answer:

/etc/X11/default-display-manager

the syntax is obvious, i'm now changing mine to read:

/usr/bin/fluxbox

However, how do I launch a persistant app?