Back links were always key. 'Quality back links' at that. High ranking websites that are relevant to your niche (or your website/articles).
However, Google's new algorithm which they have started to roll out may change this. Traditionaly people would comment on other's blogs, submit articles to sites (like HubPages) and even sign up to forum's and have their website in their signature (all creating back links). But this may soon affect your rankings if Google can see these tactics are just to 'get back links'. (Google article here http://www.activistpost.com/2011/02/new-google-alg... )
Social Networking / Media is probably the way forward. The trick is though, you always have to be good at what you do. You have to have informative information/articles that people are actually interested in. You need to crawl through the social networks and get amongst certain groups and niches until you have followers and a fan base. You keep building on this and it will be the most natural way to get more traffic because you are targeting the audience (they actually WANT to follow you and read your website) opposed to getting cheap rankings on Google where people may/or may not want to look at your site.