Follow the instructions link on backports, it's important not to click on the HOWTO link, because this leads to a blank page, you will then wrongly conclude you aren't going to find any help.
Using backports.org is very simple: 1. Add this line deb http://www.backports.org/debian sarge-backports main contrib non-free to your /etc/apt/sources.list. 2. Run apt-get update 3. All backports are deactivated by default. If you want to install something from backports run: apt-get -t sarge-backports install [package]
Where [package] is the software package we want to install.
This is a lot better than the previous solution which required the use of pinning for each package you wanted to select, this seemed a lot of bother compared to the usual use of dselect. There are instructions on use of pinning on the backports site.
Now that we know how to install a package, the only problem left is to work out the name of the package that provides openoffice2.
I managed to work out this from reading the Contents of the backports repository in my browser. For i386 architecture this can be done by looking inside this file: http://backports.org/debian/dists/sarge-backports/Contents-i386.gz The other option is to try and guess the name of the package!
I should have been able to guess the package name was openoffice.org-common. Which I installed apt-get -t sarge-backports install openoffice.org-common.