When choosing evidence to persuade a resistant audience, it is important to use sources that your audience will deem credible. Some resources/tips for discovering the source's point of view:
For periodicals (journals, magazines, and newspapers):
All SidesRates a wide-ranging number of news outlets, and gives you ratings for ones that lean to the left, center, and right.
Ulrich’s Web: Global Serials Directory Search by the title of the publication. Read the entry to learn whether the source is scholarly/academic and whether it is refereed. Find the website for the publisher and try to identify what, if any, standards the publisher has for selecting what to publish. Examine some of the titles they publish. Is there a bias?
For websites:
Google Advanced SearchDiscover what other sites link to that site by searching google for link:url. For example, to see what sites link to K-State's homepage, search Google for link:www.k-state.edu. Look at these sites to discover what they say about the site of interest.
Google the name of the author by placing his or her name inside quotes (e.g. "bill snyder"). If you get too many results, add a term or two about the author (e.g. "bill snyder" coach). Read some of the results to learn about their background, affiliations, education, etc.