As someone who usually uses the Oxford Comma I feel it important to point out there are times when it shouldn't be used, plus the basics of how to tell when you should consider using it.
The use of the Oxford Comma is generally how you tell the difference between a linked pair and a list item. A comma makes it a list of separate items while the absence makes it a linked pair (in general).
Everyone knows that you carry a bow and arrows if you go hunting with them, because one alone isn't any good. If you have a gun and a knife and you list them after the bow the list would go: He has a bow and arrows, gun, and a knife. Or the more logical way to say it would be: He has a gun, knife, bow and arrows. While a display counter in a hunting goods store would have the separate items with displays of guns, knives, bows, and arrows - thus showing each item is separate. - yes I used plurals to make it more obvious.
Most people also know the parents in the TV Nelson family are Ozzie and Harriet (linked pair = no comma), while the males in the family are Ozzie, David, and Ricky (list of three with commas). So when you have three couples coming to dinner it would be appropriate to say you were expecting Jim and Mary, Fred and Joan, and John and Jane. - This shows a list of three linked pairs.
Having said all that it's not uncommon to not have a comma when there's only two items in the list, like eating fish and chips for dinner.
My advice is to use the comma for a list of three or more items or three or more actions. I also advise people to use it when using the word and to link to phrases in the same way as you use a comma with the word but to link phrases, however I don't always do it.
Generally it's best to go with what you think carries the intended meaning the best way. I don't see it as a mandatory requirement, just something that can lead to a misreading of what you've written - which can happen with almost anything.