Yes, infomercials can be cheesy, seemingly the lowest common denominator of salesmanship. But they are also a bona fide American art form. When you study the masters, there's much you can learn. And as Web videos increasingly figure in marketing plans, more CEOs will seek to channel their inner Ron Popeils. To help them, I recently went best-practice hunting at a business that mints video sales stars: HSN.

HSN (formerly Home Shopping Network), a pioneer of TV retail, has come a long way from the days of disembodied voices extolling cubic zirconia. The $3 billion, 4,000-employee company now aims to entertain and educate rather than simply "take customers to the till" -- Andy Sheldon's description of the network's former hard-sell approach. Sheldon, HSN's senior vice president of television, says part of the network's appeal derives from the personal styles of its guest presenters, many of them entrepreneurs representing their own brands and businesses. "They are passionate, they are experts, and they connect with the audience," he says. "They believe in their products, so they create trust."

I asked HSN to send me DVDs of programs featuring some of their top-selling entrepreneur-presenters. I also enlisted two experts -- Anita Elberse and Michael Norton, both marketing professors at Harvard Business School. We met in an HBS conference room on a damp April afternoon to view the discs provided by HSN. Our mandate was to identify what made the presenters effective -- we were not passing judgment on the products. Neither Elberse nor I had previously watched Home Shopping Network, so I sat through two marathon viewing sessions earlier that week. (I drank espresso during one session and wine during the other -- a fascinating experiment I plan to duplicate on video and post to YouTube.)

Of the four presenters we watched, we were most impressed with Joy Mangano, founder of the company Ingenious Designs and inventor of the Miracle Mop and Huggable Hangers. (She sold her Edgewood, New York, business to HSN itself in 1999.) Mangano can be overwhelming -- watch her with wine, not espresso -- but "she has an intuition about what is important to consumers," says Norton. The other presenters were Wolfgang Puck, hawking his eponymous cookware; Jennifer Flavin-Stallone, co-founder of Serious Skin Care; and Andrew Lessman, whose Henderson, Nevada, company, ProCaps Laboratories, manufactures and sells vitamins and dietary supplements.

Here is a look at the marketing concepts that underlie their powers of persuasion:

But wait, there's more: Mangano reveals product features gradually, performing a home-ec version of the dance of the seven veils. Her hangers are unbreakable! They are ultrathin, so they take up less closet space! They keep a lock grip, so clothes don't fall off! As these lessons unfold, viewers have time to absorb one before being presented with the next -- the argument is like a wave, growing inexorably in power. "She makes a clear link between the feature and the benefit, and she piles them up," says Elberse. "So if you are not convinced by the first benefit, then you are convinced by the second or by the third. At some point you think, Wow, this is really an unbeatable combination of things, and you go for the phone."

Be glamorous -- but accessible: Puck is a celebrity chef. Flavin-Stallone is a former model, current wife of Rocky. But in selling mode, they feel as if they could be your friends or maybe even'¦you. Puck never tries to dazzle: He tells stories about his children and keeps the chefly flouncing to a minimum. Flavin-Stallone, who could give a hypnotist lessons in eye contact, blunts the glam with a dress-down sweater and exudes an all-girlfriends-together coziness. Her set looks like a makeup counter in the least-intimidating boutique on earth, and she mixes flesh-tone advice with confessions of her own struggles with acne. "She's like the popular senior in high school when you were a freshman," says Norton. "These people are aspirational, but they don't seem too far beyond customers' reach. The product becomes a bridge to bring the customer toward them."

You can't sell solutions unless people realize they have problems: With her dramatic before-and-after visuals, Mangano is convincing that packed closets, clothes-strewn floors, and peaky sweater shoulders are major quality-of-life issues. "She seems to have spent weeks watching people hang things in their closets," says Elberse. "You feel she understands everything that can go wrong." As Mangano demonstrates the transformation from unseemly jumble to rainbow-hued regimentation, the promise becomes a metaphor for something grander. "The real problem she is addressing isn't hanging clothes," Elberse says. "It's getting rid of the mess in your life. The solution to all that is bothering you."

Reassurance sells: Selling vitamins and dietary supplements is a tricky business. The government regulates health claims, and scary stories about ephedrine and Chinese imports have rendered the public twitchy. Against that backdrop, Lessman's company, ProCaps, claims to be the purity provider, ensuring safety by manufacturing all its own products. The segment we watched was filmed in the ProCaps plant, which could double for the spaceship in the movie 2001. The effect was reassuring: Viewers saw a real company, complete with solar-paneled roof that demonstrates concern for planetary as well as customer well-being. "The unique selling point is that this is safe," says Elberse. "We have this fully under control: There is nothing you don't want in there. He is taking away the negative."

Expertise sells, too: Puck, of course, has the advantage of legitimate celebrity. And by recounting stories of being accosted by fans in the airport, he doesn't let you forget it. Nor does he let you forget how he attained that celebrity. Puck is all about the food, preparing Gourmet-gorgeous dishes with consummate ease while maintaining a low-key shill for his cookware sets. He is also an educator -- generous with cooking tips and recipes -- and a bit of a poet (long strings of caramelized sugar are "angel hair"). That combination of reputation and demonstration carries huge credibility. Who would know better about the merits of stainless steel? My Harvard friends, neither of whom cooks, expressed doubts that "ordinary people" chop fresh herbs. Well, I do cook. And Puck had me when he deglazed a steak pan with wine and the caramelized bits came right off the bottom without any scraping.

Chew up the scenery: Mangano can barely keep still. Her face is expressive, her hands are expressive, her hair is expressive. She talks over her co-host; she seems almost to talk over herself. The cognitive dissonance between her mundane products and the evangelical fervor with which she describes them dissipates as you watch. Passion is passion. Mangano's is contagious. "The founders of companies often are terrible at selling, because they believe their product is better at a gut level," says Norton. "They don't understand they need to communicate that, to get the customer to see what they see. This woman understands."