In case you missed it, The New York Times ran an excellent article on the use and abuse of commas. Here’s an excerpt:
When an identifier describes a unique person or thing and is preceded by “the” or a possessive, use a comma:
Baseball’s home run leader, Barry Bonds, will be eligible for the Hall of Fame next year.
My son, John, is awesome. (If you have just one son.)
But withhold the comma if not unique:
My son John is awesome. (If you have more than one son.)
The Takeaway: Read the whole article and keep it on file.