In the research process not everything you find on your topic will be suitable. It is important to critically evaluate the resources you discover to ensure that you are using the most appropriate materials. Currency, relevance, author and audience, and point of view/bias are important factors that should determine whether or not you decide to use a source for your topic.
The C.R.A.P method is a guide to help you evaluate how credible and useful the sources you find will be in answering your research question, supporting your points, convincing an audience, etc.
When you look at a source (a chapter of a book, an journal article, a blog entry, etc.), ask yourself the following questions:
Author & Audience
Point of view/bias
Another factor is the type of publication, Scholarly vs. Popular. Scholarly resources are written by experts for experts. These sources are peer reviewed, have extensive bibliographies, and often contain areas for further research.
Use Google Scholar to find background information on authors and researchers.