I know, I know, the last think you want to read about is punctuation. Me, too. But I also hate being bad at things, especially things that matter.
And yes, commas matter. If you’re a writer, anyway, and I am.
After building this list, I’m learning just how bad many published works are about commas. Even my daughter’s picture books are terrible.
I hoped another blog I follow would tackle this in a fun an creative way.

They didn’t, so I’ll try. If there’s something I’m missing or got wrong, please let me know!
16 Rules of Commas
1. Use a comma before any coordinating conjunction (and, but, for, or, nor, so, yet) that links two independent clauses.
I find an example helps clarify this. EX: I wrote a novel, and I want to publish it. However, you can rewrite the sentence as: I wrote a novel and want to publish it. In this case, no comma is needed. The “independent clause” part dictates that both parts of the sentence you are joining have a subject and verb.
2. Use a comma after a dependent clause, phrase, or words that starts a sentence.
Another example may help clarify this. EX: When I finish my novel, I want to publish it. Dependent clause basically has a subject and verb, but it is not a complete sentence. Similar to #1 as it has to have a subject and verb.
3. Use commas to note appositives.
What is an appositive? The link gives you lots of examples. But here is another is case you don’t want to click. EX. The novel I wrote, a fantasy romance, is 76,000 words.
4. Do NOT use commas with appositives that are essential.
Right. So what is essential? It’s part of the sentence that you can’t do without and still get the context of the sentence. The novel I wrote that frustrated my daughter is 76,000 words. Yeah, I’m still a little fuzzy on this. But it seems if the appositive starts with “that”, it tends to be deemed essential.
5. Use commas to separate items in a series.
I wrote a novel, a poem, and a novella. Now, there seems to be some difference of opinion on the comma after “poem” in the above sentence. Those who support the Oxford comma say it should be there. Those who oppose it say it shouldn’t. Never knew there was so much controversy in grammar, did you? There are a handful of cases where you need it, and you can find the meme all over the internet.

6. Use a comma after introductory adverbs.
You know, those “ly” words all authors try to avoid after Stephen King laid down his edicts. But if you do use them at the beginning of the sentence, you also use a comma. Finally, I finished my novel.
7. Use commas to set off free modifiers that can be placed anywhere in the sentence without causing confusion.
I jumped up and down when my novel was published, laughing joyously.
8. Use a comma near the end of a sentence to separate contrasted coordinate elements.
The new author was merely ignorant of the publishing process, not stupid.
9. Use a comma when the first word of the sentence is “yes” or “no.”
Yes, I’d like my novel published.
10. Use a comma when you use a name.
Elizabeth, would you like your novel published?
11. Use a comma between two coordinate adjectives that modify the same noun.
Use commas here: The fabulous, amazing novel is 76,000 words.
NOT here: The fantasy romance novel is 76,000 words.
12. Use a comma to offset negation in a sentence.
I wrote a romance novel, not a thriller, as my first book.
13. Use a comma to separate each element in an address or in a city-state name combination within a sentence.
This didn’t come up much in my fantasy world, but I suppose it can be useful. Ex. I loved Seattle, Washington.
14. Use a comma to separate the elements in a full date and separate the date from the rest of the sentence with commas.
Again, didn’t really come into play in a fantasy romance, but may be useful to others. Friday, May 13, 2016, was a strange day.
15. Numbers.
1,000,000,000 (approximately the amount of money Disney has made selling my family Frozen princess stuff)
16. Dialogue
There are way better blog posts out there on the proper punctuation for dialogue, but as this is a comma post, here are the rules on when to use the comma in dialogue.
Use a comma when someone says something. The writer said, “I wrote a novel.” OR “I wrote a novel,” said the writer.
You’ll note that all of my examples are nice and simplistic. These rules get a lot more complicated as your sentence complexity increases.
But it at least helps to remind me of the basics.
And yes, I finally finished my first draft WIP and am tackling a revision of a different story.