The Big 5 Criteria can help you evaluate your sources for credibility:
In general, websites are hosted in domains that tell you what type of site it is.
Commercial sites want to persuade you to buy something, and organizations may want to persuade you to see an issue from a particular viewpoint.
Useful information can be found on all kinds of sites, but you must consider carefully whether the source is useful for your purpose and for your audience.
Fact checking can help you verify the reliability of a source. The following sites may not have all the answers, but they can help you look into the sources for statements made in U.S. politics.
This site monitors the accuracy of statements made in speeches, debates, interviews, and more and links to sources so readers can see the information for themselves. The site is a project of the Annenberg Public Policy Center of the University of Pennsylvania.
This resource evaluates the accuracy of statements made by elected officials, lobbyists, and special interest groups and provides sources for their evaluations. PolitiFact is currently run by the nonprofit Poynter Institute for Media Studies.