Hi, I participated in the OPW GNOME 2011 and I think I can share some experiences if you want to participate in the OPW GNOME 2012 or if you want to be a new contributor in the GNOME documentation team.
Hmmm… First at all, I suggest READ… if you want to write, you have to read!… Take your time in reading the whole User Desktop Help, read all the topics the documentation team had reviewed and improved many times… you can see the style, the common terms, and the simplest way you can explain users how to use applications in GNOME 3.x.
After that, you can see what the documentation team wants from you at the moment to write, you can check also fixed writing and good writing did by Shaun McCance and his commits. By the way, Mr. McCance created Mallard, the tool that lets you write topics for GNOME help. Practice locally in your laptop, you can integrate topics, and practice, practice, practice. Also you must read and learn!: GIT.
The last thing I suggest, is to get familiar with the GNOME applications and their help (e.g. Empathy, Evolution… ). Most of the time, one GNOME application is related with other one, so get hands dirty and play with all the buttons, menus and options that GNOME 3.x offers you… you can not imagine what surprises you can get when you do that!
Enjoy this adventure! writing is so cool as my mentor Phil Bull says “it’s definitely worth trying – you have this pleasant mix of technical precision, literary creativity and psychology. And you get a warm fuzzy feeling when you see your work translated into 50 different languages and installed on millions of computers worldwide.”