Here are the simple steps to creating a Google Mobile Sitemap:
1. Download the attached sitemap.txt file.
2. Open the file in a standard text editor and insert all the urls of your mobile site.
3. Save the file as sitemap.xml instead of sitemap.txt
4. Upload the sitemap.xml file into your mobile website folder.
5. Add a link to your mobile sitemap on the homepage of your mobile site.
The link code would look something like this:
* If you have Google Webmaster tools it is also a good idea to submit your new mobile sitemap there also.
Now when Google crawl the site they will find the mobile sitemap and know that this content has been designed specifically for mobile devices.