Use critical thinking to decide when information is useful, trustworthy, and relevant.
Searching and locating information sources is only one part of the research process. An equally important part is being able to tell if the sources you've located are trustworthy, appropriate, and authoritative.
Source evaluation happens along a sliding scale - in other words, "good" and "bad" are conditional. What you need information for and how you intend to use it is just as important as who wrote it and how experienced they are.
For example, if I want to know how many people live in Ames I can easily get a number from Wikipedia to satisfy my curiosity. But if I plan to use that number in a report then I need to verify the number using a more trusted information source, such as the latest U.S. Census data.
SIFT is a helpful acronym that describes four steps that can be used to evaluate information sources. This version on this page is a short overview that can be used for quick reference. For the full version, and for more information and guidance about how and why to evaluate information sources, see the Chapter 4 of the Library 160 textbook (open access).