There is fuller documentation of how to set up unattended upgrades on the debian wiki, but it is sometimes nice to have a super-compact "cheatsheet" for ones own reference. Others may have a use for it too.
First thing to do is to install the necessary unattended-upgrades and apt-listchanges packages. You can also configure unattended upgrades once they install. As root do
aptitude install unattended-upgrades apt-listchanges && vim /etc/apt/apt.conf.d/50unattended-upgrades
You will want to enable the emails and I like to have unused dependencies removed as well.
Set up the periodic upgrade run, again as root.
dpkg-reconfigure -plow unattended-upgrades
Then sort out the list changes config at /etc/apt/listchanges.conf.
That should be it done, check your email for upgrade runs.