I'm a big fan of the Oxford usage. In a series, use a comma after each item, i.e.
A woman should always have a great pair of shoes, a piece of semi precious jewelry, and a knock-em dead dress.
Some people insist that it could be written like this:
A woman should always have a great pair of shoes, a piece of semi precious jewelry and a knock-em dead dress.
Not according to the US News Stylebook and Strunk & White's The Elements of Style (two authoritative sources in the journalism world). The only time you don't use a comma at the end of a series is when it's names of a business firm:
Johnson, Johnson and Johnson.
So please,don't abuse or misuse the comma; it only wants to work with you.