Newsletters done well can raise far more money for charities than direct-mail appeals, according to Tom Ahern, an expert on nonprofit communications and the author of four books, including Raising More Money With Newsletters Than You Ever Thought Possible.

Mr. Ahern spelled out his views—as well as nine “fatal flaws” that nonprofit groups make with their newsletters—in a “Fundraising is Beautiful” podcast produced by Jeff Brooks, creative director at Merkle, a direct-marketing consulting company that advises charities. Mr. Brooks is also the author of the Donor Power Blog.

Charities should do more “accomplishment reporting” in their newsletters about their work and how it has helped real people, Mr. Ahern said. But instead, they produce brochures in disguise about planned giving, or they feature stories on the personal backgrounds of staff members.

In addition to reporting on their work, he said, charities should use their newsletters to promote opportunities and offers for donors to get involved or learn more and stress credibility by noting the charity’s links to other credible organizations, said Mr. Ahern. Charities should also pack their newsletters with “donor love,” language that champions donors by making it clear that they are responsible for the charity’s good works.

Another big (but common) mistake in charity newsletters: featuring a letter from the executive director on the cover of each issue, Mr. Ahern said. Such letters, much like the letters from editors or publishers of magazines, are “happy talk,” he said. They actually train recipients not to read the newsletter, he added.

Wrapping up the podcast, Mr. Ahern described one children’s hospital that revamped its newsletter and raised $50,000 from a single issue; before the redesign, each issue took in $5,000.