Relevancy
Make sure the source has something to do with your topic. You can increase the relevancy of articles you are finding by using a few search techniques.
Date
Researching a historical topic will allow you to use older resources. If the newest scientific research is needed, you will want the latest resources available.
Author/Creator/Publisher
Ask who wrote and who published the resource. Authors and publishers tend to leave their opinions in their written works.
Bias
Try to recognize the bias that is included in the article.
Your professor/instructor or librarian may give you different ways to evaluate the article, book, etc.
Note: Keep in mind to identify your target audience and choose supporting evidence accordingly.