Don’t use an Oxford comma in straightforward lists with no risk of ambiguity: The good, the bad and the ugly, NOT the good, the bad, and the ugly.

Do use it in lists of long phrases each containing their own punctuation, or in cases in which it is essential to convey the correct meaning: I dedicate this book to my parents, J.K. Rowling, and Martin Amis not I dedicate this book to my parents, J.K. Rowling and Martin Amis.

If possible try to remove the need to use an Oxford comma in your writing. 

Make sure to add a comma after place names:

The computing school will take place in Uppsala, Sweden, on 16 March.