In a series of 3 or less items, only a comma is used after the first item in the list. EXAMPLE:

I BOUGHT ORANGES, APPLES AND PEACHES FOR LUNCH.


When you have more than three items in a series, commas are used after all items prior to the "and". EXAMPLE:

HER NEW OUTFIT CONSISTED OF SHOES, SKIRT, BLOUSE, AND EARRINGS.

~~ Lolly