Wearing a green dress shirt and a purple patterned tie, Mr. Sreenivasan stressed that the course was about more than sharing photos efficiently. This was about long-term survival! As with agriculture and economic development, sustainability was crucial. “How do I do social media and keep my family intact?” he said. “How do I do social media and keep my day job?”

Left unsaid was the inverse question, the one that is increasingly nagging an entire generation of anxious, anti-Internet Nellies: Can I ignore these silly sites and keep my day job?

Tuition for the course was $495. The class would meet once a week for two and a half hours. Setting up a Facebook and Twitter account was a prerequisite.

Homework would be assigned. Twenty would-be enrollees were too late and were turned away. Demand for Facebook and Twitter instruction was booming, according to Mr. Sreenivasan. Later in the week, he would be giving workshops at The Washington Post and National Public Radio. “I want you to get in the habit of seeing things around you and using it to bring people together,” he said.

The trick was not to think too big. Earlier, Mr. Sreenivasan had been walking through the J-school and passed a board highlighting upcoming talks by Arianna Huffington and Nicholas Kristof. He sensed an opportunity for “convening power,” and snapped a photo with his iPhone. He showed the class how to upload the photo onto a Facebook fan page, and how to compose a caption aimed at sparking debate. After fielding suggestions, Mr. Sreenivasan framed up the photo as a competition between Ms. Huffington and Mr. Kristof. “Who ya got?” wrote Mr. Sreenivasan.

Next up was how to tag and untag photos and the importance of “curating” one’s online profiles. Throughout the audience, Facebook rookies followed along with varying degrees of excitement, agitation and confusion. “In social media,” said Mr. Sreenivasan, “there are no correct answers.”

NOR ARE THERE such things as social media experts, said the professor who might easily be mistaken for one. Mr. Sreenivasan has been teaching at Columbia’s J-school for 17 years and is now a dean there. During that time, he has written extensively about technology for a wide variety of publications and reported on tech issues for local TV stations in New York, including WNBC.

Recently, Mr. Sreenivasan has become something of a Twitter celebrity. He has more than 11,000 followers. Earlier this year, he told the class, he served as a judge at the Shorty Awards, which honors excellence on Twitter. His fellow judges, he said, included MC Hammer and Alyssa Milano.

The four-week course for media pros was adapted from one Mr. Sreenivasan regularly teaches students at the J-school. On the first day of those classes, Mr. Sreenivasan said, he always tells the students that if their parents found out they were paying Columbia tuition for their children to learn Facebook and Twitter, they’d probably ring up the school and call for his head on a shiv. But social media in 2010, Mr. Sreenivasan argued, was like the Internet in 1996, TV in 1950 and radio in 1912: a revolutionary medium still in its infancy. Advantages accrued to those who adapted the right technologies early. 

Mr. Sreenivasan told a story about how in 1950, Don Hewitt, the legendary creator of 60 Minutes, walked into the Columbia J-school and told the cub reporters that he would offer a job on the spot to any student who would join him at CBS television. Most of the students were wary of TV. They wanted jobs at newspapers and in radio. But the one student who took Mr. Hewitt up on his offer, said Mr. Sreenivasan, went on to enjoy a rich and celebrated career in TV.

Since social media was so new, Mr. Sreenivasan assured his class, it wouldn’t take them too long to catch up. They had fallen behind, but not irreparably so. They should all be reading the Web site Mashable.com, Mr. Sreenivasan recommended, describing it as The Wall Street Journal of social media. Recently, à la Hewitt, Mashable had shown up to recruit at the J-school. One of his students, Mr. Sreenivasan said, took a job with Mashable while turning down a paid internship at The New York Times.

The crowd gasped. “Don’t tweet that,” said Mr. Sreenivasan.

After a short break, the professor told his class that there were no hard rules on Twitter. That said, etiquette was important. Don’t Tweet more than three to five times a day, he suggested, because too much tweet from one person gets annoying. Most importantly, be concise. Twitter allows you to express yourself in a maximum of 140 characters. But Mr. Sreenivasan advised his class to use only 120—the better to encourage re-tweeting. Mr. Sreenivasan gave each student a “short tweet guide” the size of a business card, with various tips for writing on Twitter, including a list of helpful abbreviations, such as LOL for “laugh out loud” and OMG for “oh my God.”

The class was packed with accomplished New York writers. Jeffrey Kittay, the founder of Lingua Franca magazine, sat alongside a VP of communications for Sony. Nearby, there was a former top producer for CBS News, a former editor of Time Europe and a senior correspondent for AOL News.

Marie Brenner, a writer-at-large for Vanity Fair, whose 1996 article had been turned into the movie The Insider, starring Al Pacino, signed up for the class, she recently told The Observer, out of curiosity and “to learn the tools.” She was excited to study Facebook and Twitter. “For me, it’s as much a social laboratory as a necessity,” she said.

“They’re trying to drag us all into the new world—a world that took off years ago,” she added. “We all have to learn the new, new, new.” Ms. Brenner skipped the first class.

Paula Balzer, a literary agent and co-founder of a blog called Ad Hoc Mom, said she looked forward to someday telling her daughter that she’d learned Twitter at the most prestigious journalism school in the country. “It will be like telling her I went to Columbia to learn how to use a telephone,” said Ms. Balzer.

Lee Kravitz, the former editor in chief of Parade, was taking the class in hopes of harnessing social media to promote his new book, called Unfinished Business, which Bloomsbury is publishing in May. He said he already liked Facebook. Just the other day, he had reconnected with a childhood neighbor he hadn’t seen for 30 years. Would Facebook help him sell more books? “Who knows?” said Mr. Kravitz. “I’m still trying to figure out tweeting. It’s not second nature to me. But I’m soldiering on.”
Rona Cherry, a former executive editor at Glamour who now does media consulting, said she was taking the class to fine-tune her understanding of social media.

“We’re being taught here that it’s very important to keep communicating about any and everything just to build your ‘brand,’” said Ms. Cherry. “If you’re not doing that, you’re hurting yourself and your career. You’re falling behind if you’re not participating. Who knows if that’s true?”

"IS THIS STUFF SCARY, or exciting?” said Mr. Sreenivasan.

It was a week later, and he had moved on to advanced Facebook and Twitter techniques. Over the next several hours, he taught the class how to use the “lock” button on the Facebook search bar, how to create a Facebook ad and how to shorten a URL using Bit.ly.

Along the way, Mr. Sreenivasan also demonstrated a number of third-party Twitter tools, including Twitpic and Tweetstats, HootSuite and TwitterSheep. At one point, he showed how you could use a Web site called Twiangulate to find compelling people to follow on Twitter.

Now and again, Mr. Sreenivasan told cautionary tales. He showed the class a Web site called “What the Facebook?” which cataloged funny Facebook faux pas, many of which seemed to involve young people inadvertently revealing aspects of their sex life to their horrified parents. A mom told the class that her son had limited her access to his Facebook page. Heads nodded.

As the workshop wound down, Mr. Sreenivasan gave a new assignment (live-tweeting an event) and reviewed the previous week’s homework. “How hard was it to tweet twice a day?” he asked. “Anyone have trouble?” Hands flew into the air.

Mr. Sreenivasan said it was O.K. Remember the early days of email, he asked? Back then, you probably checked your email once every two days. Over time, you learned to check it obsessively. “And now you don’t get anything done,” he joked.

Give it time, he promised, and Twitter, too, would become an addiction. Get a smart phone, he said, and tweet when you’re standing in line or waiting for the bus. “Unless you get into the habit now,” said Mr. Sreenivasan, “you won’t be comfortable on Twitter when you really need it.” He paused. “Of course, you may never really need it.”

fgillette@observer.com