I subscribe to the Debian security advisory mailing list, and when new updates are released I ensure all that are appropriate are updated upon my systems.
I also use an RSS to XMPP gateway so that that the RSS feeds of Debian, Ubuntu, *BSD, etc are posted to an internal chatroom. Generally automated updates are applied every day, but sometimes it is nice to do them immediately.
(I also pay attention to oss-security, full-disclosure, etc, etc, but these tend to be less useful.)
But to be honest once you've got an RSS to email/chat gateway you can subscribe to new releases and similar with ease. So you tend to find you're updated almost by accident.