klark0 - 4:42 pm on Dec 28, 2012 (gmt 0)
Google published some guidelines a few months ago. Although they prefer a responsive design, they do support and recommend "Separate URLs for mobile".
On the desktop page, add a special link rel="alternate" tag pointing to the corresponding mobile URL. This helps Googlebot discover the location of your site's mobile pages.
On the mobile page, add a link rel="canonical" tag pointing to the corresponding desktop URL.