Term Social ranking define ranking in social search and organic search. If you like some thing on web, then whenever your friend or a person from your contact list search same thing which has been liked by you will be displayed before him/her.
You can show your interest by using Twitter tweets, Facebook Like and +1 Clicks. When your friend will search next time same thing you liked, he will get your liked website as well as organic results of his search term on first page. But actually this may be possible that your liked website is actually not ranking organically even in 4th page but your friend can see on 1st page because you liked. This is the impact of Social ranking.
That’s why, social engagement is getting more compulsory. We can at least target our known audience by social ranking.
In short I would like to say that to get social ranking, you will have to expend your networks over social networking website. At present Google is working on approx all renowned and high traffic social websites. You can do expension of your network by Twitter, Facebook, LinkedIn, +1 Button, FriendsFeed, Friendster, Ibibo etc.