When writing letters, many people simply use random salutations and sign offs without knowing that there is actually a preferred, ‘correct’ form as provided below:
If you don’t know the name of the recipient:
Yours faithfully is British usage. It is used when the recipient is not addressed by name, as in a letter with a “Dear Sirs” salutation.
Yours truly is the American equivalent of “yours faithfully”. When you begin a letter “Dear Sir,” close it with “Yours truly.”
When you do know the name of the recipient:
Yours sincerely is also British. Americans tend to reverse the order, as with everything they can get away with, and write Sincerely yours.
Sincerely is a common and acceptable close for American business letters.
Only the first word is capitalized: