Fifteen years ago, the Chronicle of Higher Education put up its first paywall. Since then, the wall’s developed lots of cracks — most of them intentional ones, as the U.S.’ most trusted voice on university and college coverage evolves its digital offerings, who it charges, and how it charges. For all the change it’s seen in those 15 years, what’s been tried seems like prologue as the company moves into the iPad and mobile age — and as it tries to figure out how best to drive up revenue in the confusing push-pull of the digital world.

“It’s like the ESPN model,” says editor Jeff Selingo. “We connect the content to what people are actually willing to pay for.” Selingo came to the Chronicle 14 years ago, starting as a reporter, and now oversees an editorial staff of 75. He knows the daily newspaper world, having worked at two before moving into the world of education journalism.

The Chronicle’s approach, while distinctive, isn’t unique. Talk to execs at the Financial Times, Consumer Reports, the Economist, the Wall Street Journal, or ESPN, and you hear the fruits of experience. They talk nuance and flexibility, not all-or-nothing paywalls.

How useful is the Chronicle’s experience to daily newspapers? Yes, the privately owned, 45-year-old Chronicle is something quite different, a high-end trade publication. (Though I do like newspaperman Pete Hamill’s description of the news business as “permanent grad school,” in his recent, highly recommended Fresh Air interview).

The trade, of course, is higher education. These are discerning readers, about half administrators and half faculty, who can be hard to please. As a must-read publication, with little direct competition (although seven-year-old online-only Inside Higher Ed is making a play for its audience and ads), the Chronicle has a market position many dailies would envy. Still a must-use for academic recruitment, from which it derives lots of ad revenue, it depends on circulation dollars for only about 20 percent of its overall income.

That said, it faces the same issues as everyone else in the print business. Three years ago, it had a circulation of more than 76,000, with 71,135 print and 5,157 digital subs. Its most recent count shows 66,000 total subscribers, but 16,020 of those are digital subs. (The Chronicle doesn’t do single-copy sales, but has expanded its site license program to colleges — so some of the “lost” subscribers now get delivery through their institution, but are uncounted.)

The Chronicle, too, is struggling with the increasingly familiar economics of transition, and with the irony is front of everyone in the business: It is reaching more readers than ever, courtesy of the web, but its business is struggling to grow.

So while trade publishing can differ from general news, the questions of how to make that digital transition, how to find workable hybrid models, and what kind of content to make free are fairly similar. The Chronicle has faced many of the same questions on pricing and access that newspapers are now knee-high into. Therein lie most of the lessons to be learned and applied in mid-2011.

It’s not a matter simply of to charge or not to charge, of allowing access to all proprietary (usually local) content or none of it. Or of setting the meter, and leaving it at a 20- or 25-article-per month level. Some of the early tests of paid digital access are stuck in a rut, as conservative experiments have retained large audiences but resulted in too little new revenue to be meaningful. The Chronicle’s nuances give publishers some new tools as some move on to Stage 2, and others are about to begin tests.

In talking with Selingo, who served on a recent ASNE panel I moderated on pay plans, I’ve picked out six key lessons from the Chronicle’s experience, collectively suggesting the newsonomics of the old dipsy-doo.

Why dipsy-doo? It’s a delightfully old-fashioned term, taking us back when people did what they could do to sell stuff. A dipsy-doo is a kind of twist, a zigzag take on getting something done. Starbucks doesn’t sell cooked coffee beans and Coke doesn’t sell brown, sugar water. They sell comfort, a piece of the good life, a good place to be.

News companies have always taken their selling too literally. They thought they were selling news, when in fact they’re selling currency, shopping deals, and packaged convenience. So, in this wannabe golden age of new digital content sales, we need to look for lots of examples of how and what newsy companies are selling. It’s not simply a matter of selling the stuff (staff-written local content) that cost you the most to produce; you sell the stuff for which people are most likely to pay you.

So, with that in mind, six learnings, down that road, from the Chronicle of Higher Education:

Check out the Chronicle’s subscription page and you see two choices. One’s a print subscription ($82.50/year) and one’s a “digital” subscription ($72.50/year). Ah, the web’s cheaper than print, you say. Well, no. The digital sub is actually a replica e-edition, complete with the same advertising as the weekly print edition. You get online access to the Chronicle’s impressive site, with either sub. You have to take either the e-edition or the paper one to get the access, though.

You can see the same kind of print/digital hybrid thinking/pricing in The New York Times’ recent digital access pay scheme. By telling readers to pay up for digital access, the Times is leading its most loyal online customers back — the old dipsy-doo — to print. Readers have quickly figured out it’s better to order some print edition and get “included” digital access than to just pay for digital access. Lead customers one way — and then do a quick turn on them.

The Chronicle, with less competition than the Times, doesn’t even feel the need to offer “online-only” subs, though it will begin offering iPad-only subs through Apple’s App Store in June, testing that new market; it has already seen 14,000 downloads of its free app.

Selingo says that deciding what will premium (paid) and what free is more art than science. “We’re deciding on a day-to-day basis what’s distinctive.” The distinctive — more than mundane work that readers are unlikely to find elsewhere — may include any kind of story, investigative piece, or data. There is a lot of free content — 40 percent of the site, estimates the editor.

The Chronicle’s front-and-center Facts and Figures section offers lots of in-depth databases (“What Professors Make,” “Who Are the Undergraduates”) and these spur lots of readership. “The power is in data,” says Selingo. “The story [often the lead-in, sum-up] is the promotional piece.” That’s a lesson we’ve heard often from Everyblock to the Sacramento Bee to Dallas’ Pegasus News to California Watch (“The newsonomics of a single, investigative story,“), but one too little implemented at dailies.

“The differentiating factor is how we visualize, how we present,” says Selingo, giving credit to Ron Coddington, a veteran of USA Today and Knight Ridder Tribune, who now serves as the Chronicle’s assistant managing editor for visuals.

It’s not just what you put where, but what you make free when. Selingo says the Chronicle will sometimes put up a big data-impressive project, making it free for a week or two, knowing that its utility will entice readers to come back over time and read it. If they come back, and it’s now premium (or paid), then they’re more likely to pay up. Conversely, some content may be paid at the outset and then become free. The bigger notion: Get readers to use — and come to rely — on the site. Usefulness precedes ability to pay. Sampling is key.

Even as it has tested, twisted, and turned its techniques, Selingo believes that a lot more nuance should be tried. He talks about pricing “pieces of content” — packages here and there, some data products, maybe niche internationally oriented modules. The challenges there: deciding what to package, how to package it and how to price it — and doing that without a major investment in time or staff. This is the mastery of the medium- and long-tail to come, probably abetted by dynamic technologies. Why not, I wonder, let readers make their own packages, and enable algorithms to price them?

The Chronicle of Higher Education, courtesy of the Internet, has an impressive funnel to work, like every other good news company. With Google, Facebook, and the rest of the relationship web feeding news sites traffic at an incomprehensible (literally) pace, it’s a matter of learning how to work that funnel on traffic. At the top end: 1.7 million monthly unique and 14.3 million page views that the Chronicle gets, according to Selingo. At the bottom end: those 66,000 subscribers.

On the one hand, that seems like an awfully small number, not quite four percent. On the other, it represents the huge opportunity of free web access, providing a constant stream of would-be customers — all monetizable to some degree by advertising, and a tiny percentage of whom who will become core paying customers.

It’s no coincidence that The New York Times’ math is similar: Get three percent of its monthly uniques to pay for digital access, one way or another, and the Times would get as many as 900,000 new subscribers.

It’s the new new math — more students needed.