As I've noted before, I've been in the Associated Press camp for decades (as a former journalist) and think it's OK to drop the comma in a simple series: She wore tan shoes, pink shoelaces and a polka-dot shirt. But as another example from the infographic shows, a simple series might not be so simple: "I'd like to thank my parents, Bill Clinton and Oprah Winfrey." Using familiar names makes that a silly example, so consider this: "I'd like to thank my parents, Bill Winfrey and Helen Clinton."
Some would say a comma after Bill Winfrey's name (or Bill Clinton's name) would tell readers that neither Bill nor Helen is a parent of the speaker.
- Most U.S. style guides prefer the comma, so use it if you're writing for U.S. organizations and publications--unless you're writing for a news outlet that favors AP style.
- If you're writing for organizations and publications in the United Kingdom, Canada or Australia, it's probably OK to drop the comma (apparently because The Economist and the Oxford University PR department omit it).
Courtesy of: Online Schools