'Yours faithfully' and 'Yours sincerely'

In British English, 'Yours sincerely' is used when the recipient is addressed by name ( example: "Dear Mr. John"), regardless of whether the sender knows him/ her or not. Americans tend to use 'Sincerely yours' or 'Sincerely'. 

'Yours faithfully', is used in a letter when the recipient is not addressed by name  ( example: "Dear Sir/Madam" ).  In a similar situation, Americans tend to use “Yours truly.”

In both usages, only the first word is capitalised.

Irrespective of the commonly accepted usages, there is an increasing tendency to use 'Best regards' / 'Warm regards' in emails.