comatose:/etc/apt# cat sources.list
# 
deb http://mirrors.kernel.org/debian/ testing main contrib non-free
deb-src http://mirrors.kernel.org/debian/ testing main contrib non-free

deb http://security.debian.org/ testing/updates main contrib
deb-src http://security.debian.org/ testing/updates main contrib

deb http://ftp.de.debian.org/debian unstable main contrib non-free
deb-src http://ftp.de.debian.org/debian unstable main contrib non-free 
comatose:/etc/apt# cat preferences 
Package: *
 Pin: release a=testing
 Pin-Priority: 900

Package: *
 Pin: release b=unstable
 Pin-Priority: -10