Have you seen these two presentations on the subject? I think they are a great start if you haven't run across them yet.
Reach a worldwide audience by building a world-ready app
APP-411T
Speakers: Kipling Knox
http://channel9.msdn.com/Events/BUILD/BUILD2011/APP-411T
Build world-ready Metro style apps using XAML
APP-528C
Speakers: Tim Heuer
http://channel9.msdn.com/Events/BUILD/BUILD2011/APP-528C
For samples, there is a XAML (C#) sample here you may be interested in reviewing as well:
Application resources and localization sample
http://code.msdn.microsoft.com/windowsapps/Application-resources-and-cd0c6eaa
A C++ sample related to this topic:
Globalization preferences sample
http://code.msdn.microsoft.com/windowsapps/Globalization-preferences-6654eb36
Thanks,
-David