LOS ANGELES — Newspapers are returning to a business strategy that served them well in the heyday of street-corner newsboys shouting the front-page news. They’re enticing people with a little free online content before asking them to pay up.

After years of offering news for free, a growing number of newspapers around the country have launched so-called metered pay walls, which give readers a few free stories online before requiring them to sign up for a digital subscription. About 300 newspapers have adopted such plans, which usually give subscribers some mix of Web, smartphone and tablet computer access.

“A lot of our customers are telling us, ‘that’s fair,’” says Rob Gursha, vice president of consumer marketing at the Star Tribune, a 300,000-circulation daily in Minneapolis.

In November, the newspaper began charging people as much as $1.99 a week for online access after they have looked at 20 stories for free. If a reader pays for the Sunday newspaper in print, however, online access can be as little as 30 cents a week. Nearly 20,000 readers have signed up.

For newspapers like the Star Tribune, it’s a second chance at digital success. As the Internet gained in popularity in the 1990s, newspapers decided to give away news on their websites while continuing to charge readers for print editions. By keeping online editions free, publishers hoped to gain enough readers to attract Web advertising.

But as readers flocked to free news on websites, many of them canceled print subscriptions. And online advertising hasn’t generated enough revenue to make up for the combined declines in print subscriptions and print advertising.

Fewer than a quarter of the nation’s 1,350 daily newspapers charge for online access so far, but industry executives are increasingly optimistic pay walls can boost digital revenue.

MaineToday Media Inc., owner of the Portland Press Herald/Maine Sunday Telegram, is studying the possibility of implementing a pay wall for its online newspapers.

Newspapers take different approaches and have different price structures. Some set a limit on the number of stories and some on the number of page views.

On their own, online pay walls won’t make up for the print advertising revenue the industry has lost the past decade. Rick Edmonds, a media business analyst with The Poynter Institute, which offers training for journalists, in St. Petersburg, Fla., says calling 2012 a turning point for newspapers and digital revenue is a “little strong.” But, he says, pay walls are one of many salves for easing the industry’s pain.

In their quest for digital revenue, many publishers have turned to Press+, a company started by entrepreneur Steven Brill and former Wall Street Journal publisher Gordon Crovitz that helps newspapers build and operate pay walls. The company says it has launched pay walls for 292 U.S. newspapers.