For individual research help, schedule an appointment to meet with a librarian.
The most scholarly academic credentials are advanced degrees (e.g., Ph.D., M.D., J.D.) in a relevant subject.
Popular sources are often written by journalists, but may also be written by someone with an advanced degree.
Look for a brief author biography in these places:
You can also search for information about the author online.
Magazines and Newspapers - magazine and newspaper articles typically provide just an author's name.
You can sometimes learn more on the magazine or newspaper website -- search for the author's name to see if biographical information is provided and also what other articles that person has written. Does the person specialize in a certain area?
Journals - look on the first or last page of the article for information about the author(s), including university and department affiliation.