Apply a four-question test (authority, currency, accuracy, purpose) to evaluate whether a source is trustworthy, and practice checking a claim by reading laterally.
Not every source deserves equal trust, and figuring out which ones do is a specific, learnable skill rather than a gut feeling. Four questions do most of the work: Authority -- who actually created this, and what expertise or role gives them standing to speak on this topic? Currency -- how recent is it, and does that matter for this particular claim? Accuracy -- can the specific facts be checked against other independent sources? Purpose -- why was this made, and could that purpose (to sell something, to persuade, to entertain) be shaping what it says?
One of the fastest ways professional fact-checkers verify a claim is called lateral reading: instead of staring harder at the suspicious page itself, they open new tabs and search what OTHER, independent sources say about the same claim or the same website. A page can look extremely professional and still be unreliable, and a page with a plain, unfancy design can still be highly accurate -- appearance is a poor substitute for actually checking.
Mastery looks like: They can apply all four evaluation questions to a real source and explain what lateral reading adds beyond reading the original source more carefully.
Common stumbles: Judging a source's trustworthiness by its appearance or confidence of tone rather than checking authority, currency, accuracy, and purpose; only reading a suspicious source more closely instead of checking it against independent outside sources.