Paul Bradshaw, a leading digital media expert and teacher in Europe, writes the Online Journalism Blog. In 2011, he wrote a post that provides a variety of basic guidelines about online verification with a section related to social media:
How long has the account existed? If it’s only existed since a relevant story broke (e.g. Jan Moir’s column; an earthquake where someone claims to be a witness) then it’s likely to be opportunistic.
Who did the person first ‘follow’ or ‘friend’? These should be personal contacts, or fit the type of person you’re dealing with. If their first follow is ReadWriteWeb, then it may be that you’re not actually dealing with a Daily Mail columnist.
Who first followed them? Likewise, it should be their friends and colleagues.
Who has spoken to them online? Ditto.
Who has spoken about them? Here you may find friends and colleagues, but also people who have rumbled them. But don’t take anyone else’s word for their existence unless you can verify them too.
Can you correlate this account with others? The Firefox extension Identify is a useful tool here: it suggests related social network accounts which you can then try to cross-reference. For companies the Chrome extension Polaris Insights does something similar for companies.