Add more content. I cannot stress how important new content is. They're moving away from traditional methods of determining what "reputable" content is. Backlinks are meaning less and less now that their technologies are improving, so now it's based on the context of the content. If they see that you're uploading more and more content related to the subject, why would it matter if you knew anything about SEO? For example, I've seen many personal blogs rise to the top in many keywords after the updates. It makes sense because - just because they don't know how to build links and how to do SEO doesn't mean they're not reputable. The best cook in the world might not have an idea about how to perform SEO, so why should his content not be at the top? In connection with social networking, that just comes with being reputable. "If your content is worth sharing, it'll be shared.", that's their philosophy. Of course one could always do that blackhat, but content will always be the main source of reputation.