Some packages aim at fast moving targets, such as spam filtering and virus scanning, and even when using updated data patterns, they do not really work for the full time of a stable release. The main goal of volatile is allowing system administrators to update their systems in a nice, consistent way, without getting the drawbacks of using unstable, even without getting the drawbacks for the selected packages. So debian-volatile will only contain changes to stable programs that are necessary to keep them functional.
1. Add volatile archive to apt sources (pico /etc/apt/sources.list)
deb http://volatile.debian.org/debian-volatile etch/volatile main contrib non-free
deb http://volatile.debian.org/debian-volatile lenny/volatile main contrib non-free
Note. Only add one of the line depending on your Debian version.
2. Update apt repository
3. Upgrade you packages