Hemant Makwana: definately, choose contents and social media
Nate Heinekamp: Content, first and foremost. Title tags are a big one, too.
Kayla Householder: Social Media and matching your tags closely with the content on your landing page. ;
Greg Kristan: Content and bounce rate. If you are writing terrible content and everyone is bouncing off your site then that is a strong signal to Google that this site or this page is not relevant and thus will be dropped in the organic listings.