There are several sites dedicated to fact-checking. When you encounter a new claim, check with these to see if someone has already investigated the claim.
When fact-checking sites don't have the information you're looking for, try a general web search on the topic you're investigating and add the term "fact check" to see if others have investigated the claim.
In addition to taking advantage of pre-existing fact checks, there are several steps you can take for better media literacy and verifying information. These strategies are from the book Web Literacy for Student Fact-Checkers:
Reading upstream is the practice of finding the original source of a claim, so you're not basing your information on someone else's interpretation. For example, if you read that the CDC suggested a strategy, go find the original CDC recommendation and verify what they actually said.
When you find information online, it's often from a source you're not familiar with. Search what others say about the source before you read their content. Is this a site you can trust? What do other experts in the field say about the author or the source in which it's published?
Research is an iterative process; information you learn while you're searching can help you search better next time. If you get stuck, go back to your original question and start a new search based on what you've learned. You might find it's easier to navigate to good information after you've got a baseline of information.