Ken Lerer, chairman and co-founder of The Huffington Post, came for a second session on media entrepreneurship at Columbia Journalism School yesterday. This time he brought with him Jonah Peretti, also co-founder of HuffPo and BuzzFeed. This session focused on SEO and how content becomes viral.

One of the most interesting tidbits that Peretti and Lerer revealed was how they use real-time analytics to determine the performance of stories, and today Nieman Lab’s Zach Seward has more on how HuffPo uses A/B headlines to see how each performs. This allows the editors to react to performance of a story and edit a headline to make it more effective for its readers and the search engines too.

Peretti wouldn’t say what the secret is with virality and it’s difficult to gauge how readers will respond. But SEO is a combination of a well written headline (this includes multiple factors and is a post on its own), well tagged for search engines, writing with SEO in mind, and easily shareable for readers (social tools, etc.).