apt.conf

[Kief Morris]

When I install a system with FAI, it pulls the unstable releases of
most of the applications, and leaves an apt.conf file on the installed
machine which seems to be the same one used during the install.
So how do I get FAI to prefer stable releases unless otherwise
specified (and is there a way to specify exceptions)? And what's
the recommended way to customize the apt.conf file on the installed
machine, should I put it in files/etc/apt.conf, use a hook, or something
else?

Thanks,
Kief