One thing that sticks in my mind is as much of a matter of preference.

For a series of objects: "American" style: A, B and C. "Oxford" style: A, B, and C. This often comes up in more complex sentences.

Used after a quote: He said, "xxx".

There are heaps of others. You can probably get a lot of good info by Googling English grammar.

*This is for the English language, which I assume you're asking about!* (Yes I did end a sentence in a preposition...)