In my opinion, key SEO factors in SEO during 2013 will be:
- HTML5 Adoption - using HTML5, CSS3 and JavaScript for creating dynamic pages suitable for any screen size
- Mobile web - specifically SEO your mobile web pages
- Local content - if you have a location-based service
- Quality content, unique content, up-to-date information
- Quality linking to and from other websites with related information and visitors
2013 is the year for mobile web, with Android and iOS being strong, Windows and Blackberry on a comeback, Firefox Ubuntu and other OS's coming out soon and 4G networks making all of these connected - mobile web will grow big this year. If your website is optimised for mobile - you will reach higher positions on mobile web searches, which will have a knock-on effect onto your desktop and tablet rankings too.