I had written a few weeks ago about my new (almost) empty xorg.conf file and explained how I had to edit an HAL .fdi file to change my keyboard layout and define my compose key.

The Debian Xstrike Force have written a complete guide on the Debian wiki explaining this input hotplug system.

I have found that there is no need to edit .fdi files, just set the following options at the end of /etc/default/console-setup:

XKBMODEL="pc105"
XKBLAYOUT="fr"
XKBVARIANT="latin9"
XKBOPTIONS="compose:lwin"

Even better, they should now be automatically grabbed from your existing xorg.conf when upgrading!