Journal articles should be submited for peer review as a matter of policy before they are accepted for publication, and books or book chapters should similarly be subject to editorial scrutiny. At the opposite extreme,
anyone can publish on Amazon without any form of editorial scrutiny unless you are willing to pay extra for it. By the same token, anyone can upload a YouTube presentation; and a high school science fair project on the subject of parallel unverses can be side by side with a presentation by a world famous physicist on the same topic. As a general rule, authors should always be willing to identify their publications with enough clarity that their credibility can be clearly established. If they become evasive or lash out when they are asked about such documentation, then it is quite likely that they have something to hide. When they are presenting at a meeting, this information should be available on the program listing; and if it is not included, then the organization itself becomes suspect.
For an exellent and highly readable overview of how science progress and changes over time, I heartily recommend this outline of Kuhn's The Structure of Scientific Revolutions, which can be read online for personal scholarly use free of charge. If you are interested in a particular author or area of investigation, Google Scholar is a much better search engine than Google itself.
If you should happen to find yourself in attendance at a meeting where the credentials and professional qualifications of the presenters are not properly vetted, demand to know their qualificarions or demand your money back. It's that simple.