Use the Oxford (or serial) comma, the comma that precedes the and or or in a series. Omitting the comma, as is commonly thought to be correct, can profoundly change the meaning of a sentence.
The greatest influences in my life are my sisters, Martin Luther King and Gandhi.
The greatest influences in my life are my sisters, Martin Luther King, and Gandhi.
The first sentence implies that you have two famous sisters, neither of whom are women. The second sentence correctly identifies the three important influences in your life and does not make you appear to fail to understand men are not sisters.
Another example of omitting the serial comma confuses the world’s greatest party with one that only the oddest fetishist might choose to attend.
We had a party, and we invited the strippers, JFK and Stalin.
We had a party, and we invited the strippers, JFK, and Stalin.
