First question: why do you need local Debian-based install inside your Debian distro? Sometimes you want to check some experimental packages and don't want to break your base system or start some service in isolated environment without virtualisation effort. Then chroot comes as an effective solution for you!
First of all you have the debootstrap program that is used to do all the job you need:
sudo apt-get install debootstrap
sudo debootstrap --arch i386 squeeze /home/debian-chroot http://ftp.debian.org/debian
And you jump to your newly-installed system:
sudo chroot /home/debian-chroot
And: voila! Done!