I have many sites and depending on which one I am talking about, the top two sources of traffic are from search and social media. Some get more returning visitors than others. It's related to exactly the type of site I am looking at.
All of the things that you've mention about are primary source of traffic, but upon checking the google analytics I can say that most of the traffic comes from organic search. The typical things that we are required to do is of course do link-building so that the website will be more visible to a lot of users. Social media fan page promotion also works.
I have been doing SEO for a while and now I`m getting my most traffic from organic search engine. It`s not too much but it`s top quality and targeted traffic. Also I tend to receive some visits from social media website like Facebook and Google plus.
At first, most of my blog traffic came from ads on facebook and google +, but after producing quality content and getting an audience that was interested in my articles, the biggest traffic is now coming from search engines like example Google and some of Bing.
Mostly the fast traffics comes on website from Forums you can build back links from forums sites so that it is one of the important part of maintain DA-Domain Authority of Sites, Using a Digital channels like Linked in, Instagram, Face book & G+, Pint rest I will be Suggest to you can use automated tools like Hootsuite
Traffic sources vary depending on the niche. I have a gaming website that has 90% of its traffic coming from just Reddit. At the same time, I have a cryptocurrency blog that mostly has traffic coming from search engines.