Updating a pre-existing Debian package
This article was first written in December 2005 for the BeezNest technical website (http://glasnost.beeznest.org/articles/314).
From time to time, you would like to have a more recent version of an application than what is currently packaged in Debian .
This is basically the same process as backporting anyway.
There has been the introduction in Debian of a new set of tools called Debian External Health Status (dehs) which proved really useful for QA. This set of tools involve a file called debian/watch in the source package, and when this file is present (and working), the utility uscan  may be used to serve our current purpose.
So, we’ll download the sources of the latest version available (you need of course to have the right deb-src line in your sources.list
$ apt-get source packagename
It will download and extract the sources package in a directory whose name will be packagename-X.X.X and apply the Debian packaging patch  to it.
Then go into the newly-created directory and issue the following command:
~/packagename-X.X.X$ uscan --verbose
It will try to get the latest upstream tarball and extract it in ../packagename-Y.Y.Y/  and will try to apply the old Debian packaging patch to it (while trying to automate some stuff like the release version in debian/changelog).
If everything went well, go to the newly-created directory ../packagename-Y.Y.Y/ and issue the following command (if you want to modify something in the packaging, this is the good time to do it):
No doubt it will ask you to install some build-dependencies. Just read the output and install them accordingly. Relaunch debuild if needed, and enjoy your new package!
 I’m talking here about Unstable, because otherwise it’s probably just plain backport, and don’t forget Experimental exists, and may already host the application you miss so much
 part of package devscripts for some time already, and I suggest you install package fakeroot too
 it will tell you exactly