The key to identifying trustworthy sources, whether you are finding them on the web or anywhere else, is thinking critically about (1) who created the source and why and (2) how that person or entity's qualifications and purposes relate to the question you need the source to answer.
High quality information is expensive to produce, and in most cases, the people or organizations that produce it want to be compensated for it. Lots of the world's best quality information requires that you buy a book, subscription or membership, or even be an employee of a particular organization. Search engines like Google have limited access to the information that is behind paywalls, and no access to private areas of the internet. Think, for example, about the MMA public webpage vs. all the information you can access about course schedules, grades, and financial information when you log-in to your account. The latter information is available via the internet, but it is not on the open web, and it has not been indexed by search engines.
There are lots of research techniques that don't involve typing a keyword search into a website, but it is useful to consider some of the differences between those that do:
Search Engines (like Google):
Database Searches (like those built-in to Business Source, ScienceDirect, or JSTOR):
Discovery Layer Searches (like Sea Search on the MMA Library website):
None of these types of searches is inherently better than another, rather, they are suited for different research tasks. Google searches and discovery layer searches are particularly good for early, exploratory/background phases of research. The further you get in your research, the more you want to narrow your searching to specific repositories of information that you have already identified as reliable, such as a subject-specific database or a particular website.
One of the things a Google search is always good for is investigating the credibility of the author of another source. Use Google to figure out where someone works, what they studied in school, if they've ever published on a particular topic, or what an organization's mission is, how it's funded, or what other people in the field think of it. All of these answers are relevant as you consider how and why a given information source came into existence.