GDM Step by step...please!

[Lee McLain]

Hi everyone,
     Could someone in the know please provide a step by step list of
what files are being executed when logging into GDM?
     For example:
1. After entering a valid username and password, SCRIPT X is then run.
2. SCRIPT X genereates a variable and passes it to SCRIPT Y, when then
determines a result.
3. That result is passed to SCRIPT Z, which then finally executes the
window manager/desktop environment chosen.

     Yes, that sounds like hand-holding, because it is!  I can't find
a step through for the Ubuntu way of starting X.  The only thing that
I do know is that they do it a bit differently than others!
     I am trying to find an appropriate place to launch my dockapps
when running Fluxbox.

Thanks,
Lee