A reputable news site will have a date when a story was published, make sure you check to see when it was published. More importantly though, check it's sources and see what date they were published. Stories that go viral are often based on old, out of date, information that has since been superseded.
Evaluating each website you use is an important way of ensuring the information on it can be trusted. There are a few simple ways you can easily check how reliable a site is:
Who made the site?
Look for an 'About' page or details of the creators - this is often found at the bottom of the home page. Also look for contact details to see if a website can provide details of who made the content.
Websites should be able to provide references for statements or quotes, check to see if a site has provided references and follow them up. Websites such as Wikipedia may provide references but you should check my following URLs or looking in the printed source referenced to ascertain the accuracy of the source. Fake news websites often give erroneous references that lead nowhere.
Most websites have adverts now, it's how they make enough money to keep the site online and employ staff, but always think carefully about websites that have adverts. Think about whether the people who placed the adverts have any influence over the content of the site.
Check to see if the information you're looking at has been verified by anyone else. Is the website peer reviewed in the same way an academic journal has been? Do a search to see if anyone has published an article responding to the news you're looking at, you may find rebuttals or analysis elsewhere to confirm the information.