:/# cat  /etc/apt/preferences.d/repo-priorities.pref
Package: *
Pin: release v=*,a=stable,c=main,o=Debian,l=Debian
Pin-Priority: 990

Package: *
Pin: release v=*,a=wheezy-backports,o=Debian,l=Debian
Pin-Priority: 490

Package: *
Pin: release v=*,a=testing,o=Debian,l=Debian
Pin-Priority: 480

Package: *
Pin: release v=*,a=unstable,o=Debian,l=Debian
Pin-Priority: 450

Package: *
Pin: release v=*,a=experimental,o=Debian,l=Debian
Pin-Priority: 400

Package: *
Pin: release a=trunk
Pin-Priority: 400

Package: *
Pin: release
Pin-Priority: 300