The Wall Street Journal has long been successful charging for content. Now it plans to charge for more. Executive Editor of the Journal Online Alan Murray told Zachary M. Seward of Harvard’s Nieman Journalism Lab that the site will begin targeting a subset of subscribers with a “premium initiative” to sell “narrower information services” at a higher price. The first products will likely be centered around energy coverage and a news service aimed at CFOs.

Other highlights from the interview:

– The best model is a mix of paid and free content. “It’s not pay wall/no pay wall,” Murray said. The Journal allows free access to all of its political, arts, and opinion coverage, in addition to certain breaking news stories and all of its blogs. But the rest of the site requires a subscription.

– You can’t charge for exclusives that will just be repeated elsewhere. “If it’s a big news story, if we report a takeover and – we could hold that behind the pay wall, but if we do, BusinessWeek or someone else will simply write a story saying ‘The Wall Street Journal is reporting x,’ and they’ll get all the traffic,” Murray told Seward.

– Don’t charge for the most popular content on your site. “That’s been the mistake that some people have made in the past,” Murray said. Items with broad appeal are better used to build traffic that can be turned into advertising revenue.

– Content behind a pay wall should appeal to niches – for example, coverage of high school sports. “To the people who want to read it,” he said, “they really want to read it because maybe their kids are involved. Maybe they’re willing to pay for that or maybe there’s a photography service that’s connected to that where you can download pictures of your kids or of the game. But only if you’re a subscriber.”

You can watch the full video interview here.