These are not web design guidelines, rather 2 specific user experience points, that have influence over search engine optimization. When you design your site keep these in mind.
It is an important factor because your visitors are using devices of various size. And their experience with your website matters to search engines. 3 available methods: You may change the user agent in your server or use a different url for mobile browsers. But most useful method from seo perspective is to use a responsive web design (wiki article on it). here is a vast resource is available for mobile seo and a tool to check if your page is mobile or not.
4 major factors for perfecting mobile specific seo.