Last I was meeting with a couple of writers from our local writing group, Write by the Rails (website: http://writebytherails.blogspot.com/), as we were working on edits for our projected anthology. Suddenly (which is how this sort of thing usually happens) we started talking about the Oxford comma and how each of us favored it as a means of punctuating items in a series.
In case you haven’t heard of the Oxford comma, you probably have been using it. In a series of items, if a comma is placed before the “and,” it is called “an Oxford comma” (or domestically, “a Harvard comma” or if you prefer, “a serial comma”).
Recent usage has eliminated the final comma, which can result in ambiguities such as:
I’d like to thank my parents, John Donne and God.
Probably John Donne and God are not your parents. The Oxford comma clarifies this bit of confusion:
I’d like to thank my parents, John Donne, and God.
There’s a good article on the subject at http://en.wikipedia.org/wiki/Serial_comma, with many more examples and enough ambiguity to confuse anyone.
We editors and writers like the Oxford comma, although using it is a matter of assuring clarity and economy. That’s why I say you’re on your own. Look at the meaning of the series and do whatever it takes to make it clear.
I tend to favor it because I worked every grammar exercise in the Warriner’s series for six long years and they of course liked the serial comma long before it had the name of Oxford. Still, we want to keep up with the times. But we also want to be clear. Good luck to you and be careful out there!