Who is the Author? What are His or Her Credentials?
Check the library catalog also to see if the author you are considering is listed in any specialized reference works such as Who's Who, Contemporary Authors or American Men and Women of Science.
Inclusion in reference works such as these does not necessarily guarantee their trustworthiness, but it will provide you with a more informed idea of the author's background.
When your source is a weekly newsmagazine like Time, Newsweek, or U.S. News & World Report, the author is likely to be a reporter who is neither famous nor world renowned.
Though weekly news magazines do occasionally feature articles by experts, and all have solid reputations for careful fact-checking and presenting fair ranges of opinion, be aware that some select facts that mirror the opinion of their editors.
When getting information from the World Wide Web, online newsgroups and certain electronic databases, it may be difficult to find and evaluate the author's credentials. If they are not provided, consider emailing the author with a formal inquiry.
Above all, when in doubt, carefully consider whether using a particular author's information is worthwhile. Weigh the pros and cons.
Ultimately, the best measure of someone's authority is whether their work meets the standards and critical demands of other recognized authorities. Ask your instructor and other knowledgeable experts on campus what they know about the author.