Hi,
Debian begins with /etc/rcS.d/ scripts and then run /etc/rc5.d/ scripts (if you boot into runlevel 5 of course). If you want to add your own script, edit it in /etc/init.d (don't forget to set exec rights) and then do a symlink like that:
Code:
ln -s my_script /etc/rc5.d/S90my_script
Note that when your system reboots, it uses /etc/rc6.D/ scripts and if it halts that's /etc/rc0.d/ one's
Oliv'