PolicyMic’s founder explains that boosting site traffic comes down to doing three things well.

In 2011, Chris Altchek left his job at Goldman Sachs. He created PolicyMic, a site that used Bleacher Report’s model of hiring mostly-free contributors to produce content and applied it to politics.

Since then, Altchek and his co-founder Jake Horowitz have raised a small family-and-friends round followed by $1.5 million from angel investors and VCs.

The team recently grew to 16 people but Altchek says his team reached 6 million monthly uniques with just 12 people prior to the mini hiring spree. Part of the traffic growth came from obvious tweaks, like adding more apparent share tools to the site and expanding into other verticals, such as news and entertainment. There’s also an obvious traffic spike in March 2013, when PolicyMic closed its financing round. Other less obvious factors contributed to the company’s growth as well.

We asked Altchek which moves he’s made over the past few years that helped his site grow the most.

“PolicyMic focused on a very specific demographic–millennials–and a specific type of content–high-quality analysis,” Altchek says. “We’ve been able to grow traffic to over 6 million monthly uniques, which is now 1/3 social, 1/3 search, and 1/3 direct, by doing three things really well.”

Here are those three things, according to Altchek:

Smart social: We’ve narrowed in on smart content that people still want to share. We hired a behavioral scientist from London School of Economics, Liz Plank, who’s job is to study viral trends on smart topics. We track social sharing on all the top publishers on the web and draw trends that allow us to produce viral stories on important topics. A few examples include this story on the protests in Turkey which has 97,341 shares, or this story on Calvin & Hobbes with 50,011 shares, this story on Brazil which 71,570 shares, or this story on the American economy with 47,176 shares.

Mobilizing millennials: We have built our editorial team around our millennial contributors–who are the leading 20-something in their fields. Instead of writing multiple stories per day, our 12-person editorial team is focused on training writers, editing, fact-checking, and recruiting millennials with deep topic expertise. By sourcing these high quality millennial contributors, we have built out a network that produces, consumes, and distributes to have an impact on PolicyMic and across various social networks. Our contributor model has allowed to us to scale to publishing over 90 high-quality articles per day.

Viral Engagement: While building a high-quality publishing system, we’ve built a community of millennials that want to have intellectual discussions on big ideas. Because of the authentic discussion happening on our platform, thought leaders have begun holding Q&A by publishing on the site and responding to comments. Here are a few recent thought leaders we’ve hosted:

Future improvements Altchek is planning to make include a site redesign, and the expansion into even more verticals this fall.

To see how he got started, here’s a Q&A with Altcheck shortly after he left Goldman Sachs.

This story originally appeared on Business Insider.