The Oxford Comma Imperative
As per Strunk & White's The Elements of Style:
In a series of three or more terms with a single conjunction, use a comma after each term except the last.
|red, white, and blue|
|honest, energetic, but headstrong|
|He opened the letter, read it, and made a note of its contents.|
This is also the usage of the Government Printing Office and of the Oxford University Press.
In the names of business firms the last comma is omitted, as
|Brown, Shipley and Company|
The abbreviation etc., even if only a single term comes before it, is always preceded by a comma.