There are various ways to get traffic to a website which includes:
What’s your personal favorite source of traffic?
Academic sites.
Yes, I am fully aware that Google doesn’t care about the domain extension when it comes to ranking, and academic institutions and government bodies don’t have any additional link power. What I have noticed, however, is that because it’s now assumed that they have no extra power most people completely ignore them. If regarded as just a normal website they have a ton of backlinks and more often than not their external links are in prominent places.
At a previous company I emailed a bunch of universities and colleges about our website and how a link to us (in their hospitality sections) would help them out and around a quarter of them obliged if we linked back. Not only did we get some fantastic links, but people clicked through and used our service, and the link spread throughout other universities where we operated and to other businesses.
All it took was some backlink research on our competitors and we had some great, relevant traffic each time a conference was held at the university. It also did our rankings a world of good too. I’m now at a different company, but once again a huge contributor to our service is, you guessed it, a university website.
The one of those that I won’t ever get is PPC 
Beyond that, I don’t really care where people come from. If they come as direct traffic then the chances are they are repeat visitors, and that’s good. If they come from referrals (I assume you mean links from other sites?) or social network links, that means that there are other people out there linking to my site, and that’s good. And if they come from search engines, that means I’m near the top of the rankings, and that’s good too.
favorite source of traffic is search engine traffic
New direct traffic is the highest converting because that is usually word of mouth or advertising that interested someone enough to type in your url.
After that search engines are the best source of traffic to get highly targeted customers. When a customer is looking for your product and service and you are right in front of them then you have a great chance at acquiring a new customer. There are always people searching for what you offer so search engines should play a major part in your marketing.
I do like referrals. That is a great way to create business because it is usually performance based so you can control your ROI. As long as you give good incentives.
Social media will be getting bigger and bigger for advertising. Word of mouth has always been the best way to advertise and with the right viral campaign, social media can spread word faster than anything. But, you can also spend a lot of money and get nothing.
direct and SE traffic IMO is best.
then again we need traffic from as many sources as possible to bring in prospective repeat users.
favorite source of traffic is search engine and direct traffic 