Research the author when you come across a paper or an article on a private website or blog. The author's level of education is one way of determining the reliability and credibility of information. If the paper or article is written by a mainstream economist, for instance, it is likely to contain authoritative information.
Check when the work was published and updated. Information published a decade ago might be stale if it has not be updated since. Compare the information with scholarly databases to establish whether the information is usable the way it is. Scientific research information must be current, because the many topics evolve all the time. Old information is useful in humanities, but even then, the information should be double-checked.
Evaluate the publisher. Information published by an academic journal is likely to be more credible than on an opinion page of a news website. Much of the information on mainstream news sites is credible, but be weary of information from op-ed writers, even it is published on the website of a renowned news organization. News articles published by credible news organization are generally reliable.
Look at the source's source. An article citing other reliable sources is usually credible. But you must verify the source's source, too. The author might, for instance, try to promote a point of view by using only sources that support it. If the article is based on new information, look at the credentials of the author and the publisher. The organization with which the author is affiliated matters.
Check the intended audience by looking at the table of contents or reading the first few paragraphs. An article targeting a certain political fringe group, for instance, is unlikely to be objective. Pay attention to consistency in the article. An imbalanced presentation is either a sign of incompetency by the author or an agenda.