One of the most challenging tasks in doing research is properly incorporating sources. Here are some helpful handouts that you can use.
Questions to ask:
Is it a university press -- in which case the material is more likely to be scholarly -- or a well-known publisher?
That is, are the author's ideas supported with research documented by footnotes, a bibliography, and/or a works cited page?
The "Five Criteria," used for evaluating WWW sites, can be used when evaluating information from any source (magazine articles, books, newspaper articles, etc.)