Sometimes fake news can appear in the form of a tweet, normally from a fake twitter account. There are a few things you can look for if you suspect it to be false...
1) How long has the account been active? If the account has only been active a short time, especially if it's a organization or person who is well known, than it's a sign that it's probably fake.
2) How many posts does the account have? If there's only a few posts on the account, especially if from something well known (i.e. New York Times), it's another sign that it's fake.
3) Does the screen name and URL match? For example, if the URL is something like "twitter.com/john-doe," but the name in the profile doesn't match that, it's probably a fake profile.
What you see above is an example of fake news you might find on Facebook. Here are some tips for making sure the stories you see are not fake.