Check the account history of the source. Two red flags are: the number of posts and how long the account has been active. If it claims to be a well know source(like CNN or CBS) and only has a few posts in its history that is a clue. If it's a well know source and the account has only been active a short time that is another red flag.
Images of an event are often reused to deceive people. You can check if an image has been used before on a reverse image search service like TinEye.
The Twitter website offers a lot of information about verifying Twitter accounts. Check out the page here. The first rule on this page is
|"Just because it's on the internet doesn't make it true. It seems so simple, but if everyone knew that, Facebook and Google wouldn't have to pull bogus news sites from their advertising algorithms and people wouldn't breathlessly share stories that claim Donald Trump is a secret lizard person or Hillary Clinton is an android in a pantsuit."|
In his recent article, A.J. Willingham gives the top ten ways to determine if the news story is fake.