I've always taught students that when composing a list you must include a comma after each item. This includes before "and" and your final item.
Example: Jane likes apples, bananas, and oranges.
I've been told this is incorrect. I've been told this is outdated. I do it anyway.
Recently, thanks to the wonder that is shared photos on Facebook, I've learned that my usage of that last comma in a list is called the Oxford comma, and today I'd like to dedicate my blog post to that endangered comma.
Oxford Comma, this one's for you!
And finally, I'd like to share the importance of all commas everywhere.