Check the source first
Before the content, look at who published it. Is it an organisation with a name, an address, a corrections policy and named authors? A site you have never heard of with no contact details deserves more caution than a long-established outlet, though even established outlets make mistakes.
Look for the original
Many stories are second-hand: someone read a report and wrote about it. Find the primary source, whether that is the study, the official statement, the court document or the recording. If a story says 'research shows' and never links to the research, treat the claim as unconfirmed.
See who else is reporting it
A real event is usually covered by several independent outlets. Search for the key facts and see whether other reputable sources report the same thing. If only one site carries a dramatic claim, wait. Genuinely big news does not stay in one corner of the internet for long.
Check the date and the context
Old stories are often recirculated as if they were new, and photos are reused from unrelated events. Look at the publication date, and if a picture is central to the story, a reverse image search can show where it first appeared.
Watch for emotional pressure
Stories designed to spread quickly tend to be urgent, outraged or frightening, and they ask you to share immediately. That pressure is a signal to slow down. The more a post wants you to act before checking, the more checking it needs.
Be honest about what you cannot verify
You will not be able to confirm everything, and that is fine. The responsible option is to hold the claim loosely, not repeat it as fact, and wait for better evidence. Saying 'I am not sure yet' is a perfectly good position.