Finding sources is one thing -- evaluating whether the source is useful depends on whether the source is credible and provides facts or expert opinion appropriate for your research question.
For quick tips to help help judge the trustworthiness of all sources, check out this video from NCSU Libraries.
Currency - The timeliness of the information.
Relevance - The importance of the information for your needs.
Authority - The source of the information.
Accuracy - The reliability truthfulness and correctness of the content.
Purpose - The reason the information exists.
For a great introduction geared specifically towards the evaluation of websites, check out this video from the Community College of Vermont's Hartness Library!
Douglas D. Schumann Library & Learning Commons
Wentworth Institute of Technology
550 Huntington Avenue
Boston, MA 02115