Helpful criteria by which to evaluate the information you find, and questions to ask in your evaluation:
Who is the author of the material? What are the author's credentials? Who is the publisher of the material? Is that publisher well-known?
Is the information presented in an objective manner? Are all sides of the issue presented? If not, can you determine the side of the issue the author takes? Does the author acknowledge a bias? Is there any inflammatory language in the material? Does the author verify statements with facts and cite his or her sources? Does the publisher stand to benefit from any research published (i.e. a drug company funding a study on its own products)?
Does the author cite his or her sources? Does the material provide a description of its research methods? Does the information contradict other published information?
When was the material published? Does this work have a more current edition or update? Does your topic require more up-to-date information (i.e. is it a scientific or medical topic or about a current event?
Does the information add to the topic you are writing about, or is it peripheral to your discussion? Is the information significant and valuable, or trivial and common knowledge? Does the material provide references which will also be useful?