Whether you're on a blog, reading comments in a Reddit thread, browsing images on Pinterest, you're evaluating the information. Based on your interests or information needs at the time, you evaluate the piece by who posted/pinned (their knowledge or skills), the quality, the currency, its genuineness, and so on. When you research for an academic project, you employ similar techniques of evaluation. You will determine whether a resource is appropriate for your paper, credible, reliable, and authoritative. 

The following list will assist you in developing a strategy for critically evaluating sources:

• Quality of the resource: is the resource free of spelling, grammatical, factual errors, formal vs. informal language?
• Cited sources: does the source provide a list of their sources? Note that some resources, such as newspaper articles or magazine articles typically do not cite their sources. In this case, use the other criteria to determine reliability. You will have to determine if a newspaper or magazine article is an appropriate source for your paper. 
• Author's credibility: what is his/her expertise on the topic? Have he/she written about this topic before? Does he/she have an advanced degree (such as a Master's, J.D., or Ph.D) in the discipline? Do other authors refer back to this author? What is his/her reputation?
• Publisher credibility: Was the book or article published by an university press? Examples include Oxford University Press, Harvard University Press, MIT Press, University of Nebraska, etc. If it was an university press, then it is most likely a peer reviewed source, which means that other experts, the author's peers, reviewed and evaluated the piece before it was published. Books and articles published by popular presses or published in popular magazines may also have respectable reputations, but their purpose is to reach a general audience and not to communicate scholarship, so you will have to decide if those resources would be the most appropriate for your research. 
• Objectivity: Is this resource biased? Are the opinions supported by evidence? Are the writer's opinions based on fact (supported by evidence) or is he/she opinion based on emotions or untested ideas? Is this piece presenting a verifiable perspective or is it propaganda? 
• Currency: How current is the information? Could there be more current information? 
• Determine the information you need: Do you require a brief overview of a topic? Or, do you need more detailed, extensive information? If you only need a brief account or overview, a newspaper or an entry in a reference book may be sufficient, but if you are writing a research paper, you may need to locate academic sources, such as a peer-reviewed article or book.