1. Determine what kind of source it is: primary or secondary
2. Your sources need to have an author and bibliography, or, need to be from an accredited institution (like .gov, .edu, or .org) or a informative book that has valid research and data from author(s)
3. Look at the author's sources on the bibliography.
4. READ the information and then compare to other sources. Does the information make sense? Does it compare?
5. Check out Purdue University's Writing Lab site on how to find credible sources: https://owl.english.purdue.edu/owl/resource/588/02/