The comma. So tiny. So cute. And yet the cause of so much mischief! Why are commas so difficult, anyway? Why does it take so much work to figure out whether or not to use one? It's not you - it's them! There are dozens of rules about comma use! No wonder these little marks are such perennial punctuation pitfalls.
What I'm not about to do is list every single rule for using a comma ever. I don't think you want to sit through that list. Instead, here is the one rule to rule them all.
No Rule, No Comma
If you can't think of a reason why that comma goes there, skip the comma! (The rule I just used is that a comma has to follow a dependent clause that starts a sentence - see Rule 5 about introductory clauses.) This might sound like the worst tip ever - "Does she really expect us to memorize every single comma rule?!" But you have to follow this one because the most common misuse of commas is over-using them. Many people say, "It just seemed like there needed to be a pause there, so I put a comma in." NOOOOOOO! This does not qualify as a rule! I'm going to give you some basic categories of rules below, and you're going to use those as landmarks as you decide where and when to use commas. There is also a caveat at the end of the rules that you have to read, because, like every other aspect of language, the rules of comma use have exceptions.
So, let's get started. In order to use the one big rule, you need to learn some smaller rules. Here are 6 places where you do, in fact, need commas.
1. Dialogue & Direct Address
These are possibly the most boring uses of commas, but that's because they are no-brainers. No-brainers are great because you don't have to decide! Any time you introduce speech, you must use a comma to set off the dialogue from the rest of the sentence.
Jim exclaimed, "Commas are my least favorite form of punctuation!"
"I know what you mean," agreed Caroline.
"Well," interjected Suzanne, "I don't think they're as confusing as semicolons."
Additionally, use a comma when you address someone by name. This often occurs within dialogue.
"Suzanne, have you been reading ahead in the textbook again," queried Caroline.
"No, Caroline. I was born knowing about semicolons," retorted Suzanne sarcastically.
2. Numbers, Dates, & Addresses
More no-brainers! Horray! You probably use commas correctly all the time when you write numbers larger than 999, and when you write the date. Writing out an address in a sentence is less common, but you can easily memorize where the commas go: after the street and after the city.
On June 14, 1724, the pirate captain stole $13,892 worth of gold bullion. He then sent it to his cousin at 100 Gooseberry Ln., Oxford, England.
Got three or more items in a list? Separate them with a comma.
Pirates enjoy pillaging, plundering, and pilfering.
What about more than one adjective to describe the same noun? As long as these adjective are of the same "power", you need commas. Adjectives are equal if you can switch their order and the sentence still makes sense, or if you could replace the comma with "and".
The pirate ship was a long, delapidated vessel.
4. Interruptions & Extra Info
Adding extra information with a phrase or clause? Interrupting one thought to add another? Use a comma to show where the main thrust of the sentence and the extra bits intersect. This includes non-restrictive phrases and clauses, words that show emphasis, and appositive words and phrases. If you can take the word, phrase, or clause out of the sentence without changing the meaning, you need the comma! (That's all non-restrictive means.)
Pirates, for example, are popular figures, despite their dastardly deeds.
5. Introductory Words, Phrases, & Clauses
Use a comma after a transition word, or after a phrase or clause that shows the conditions or reasons for the action in the main part of the sentence.
Unfortunately, pirates are a very real threat in some parts of the world today.
As a result of kidnapping, many people in impoverished nations are forced into lives of piracy.
Unless the underlying issues of poverty are addressed, it is unlikely that piracy can be curbed.
6. Compound Sentences
Sorry, I used a grammar term. But you can easily spot a compound sentence: it has two subjects and two main thoughts. Each subject has its own verb(s) after it. The two parts of the sentence are connected by a coordinating conjunction: for, and, nor, but, or, yet, so.
The myth of pirates is enticing and exciting, but their reality is violent and horrific.
Six rules. That's not bad. And now here's the caveat.
Sometimes you need a comma to make the sentence more clear. If two thoughts run together, use a comma to separate them. Use your judgment and a comma to help you clarify ideas and demarcate them. But please, whatever you do, don't stick in a comma because you think there's a pause. And help yourself by learning about conjunctions so that you don't end up sticking solitary commas into sentences when it turns out they are supposed to be accompanied by joining words.