First thing to do is ask whether mobile visitors are interacting with your site differently than desktop users?
> Go into Google Anaytics and segment out the mobile traffic. The mobile segment might include Tablet traffic so be aware of that figure. Once you have the data, focus on landing pages, conversion rate, and where people leave the conversion funnel. Optimize accordingly.
Best practice tip: Its always a good idea to add a mobile XML site map and submit it to Google and Bing.