Once you've mastered the comma, most English grammar books ask you to consider the semi-colon. Please don't. Semi-colons are pretentious, and they serve no needed function, except in one very limited example. The rule says, when you have two independent clauses (two subjects, two verbs) you can join them with a conjunction or a semi-colon. But only academics use them that way; if you're writing fiction or guidelines that you want to be useful, stick with conjunctions. (There, now. Didn't that sound stuffy?)
Only use a semi-colon in one instance -- in a series, in which each item has a qualifying phrase attached loosely to it. Consider this sentence and its variation:
"I invited Eric, the boy in the blue shirt, Emily, a friend who plays the piano, Joshua, a neighbor from down the street, Sam, the kid nobody likes, and Sally." (How many people received an invitation? 9 or 5?) If you leave all the commas in, like this, you mean you invited 9 people, some of them with names and some with identifying tags.
"I invited Eric, the boy in the blue shirt; Emily, a friend who plays the piano; Joshua, a neighbor from down the street; Sam, the kid nobody likes; and Sally."The punctuation is correct here, but it, too, looks like an English teacher wrote it. (And remember, nobody loves an English teacher.)
When you are tempted to use a semi-colon, take a break from writing. Your readers will thank you for it.
There. I just used one, but you didn't need it to know that the word colons was a subject heading, did you? If I could, I would abolish all colons from informal or fiction writing. Why? Because they fail to meet the primary definition of a punctuation mark. Hmmmm? You've forgotten already, haven't you?
Punctuation marks were invented to help oral readers know when to breathe or when to stop talking, or when to raise the tone of the voice at the end of a question. The colon can not be pronounced, or breathed, or indicated by tone of voice. The only thing it says is "A list is coming." And lists have no business cropping up in fiction. As a writer, you can be much more creative than that.
Now see what we've accomplished? We've eliminated the need for a whole key on the QWERTY keyboard. If I could, I would replace it with a much more useful one -- your favorite expletive, for use every time you mistype a word or accidentally delete something important. (I once found a stick-on key with a four-letter word printed on it. It was non-functional, but a great stress-reliever. Before I finished my first book, I had pounded the lettering right off it.)
We can't do away with these entirely, but like the semi-colon, I recommend that you use them as if they were as expensive as diamonds. One diamond, no matter how small, glitters and looks beautiful. Put a hundred of them in a pile, and they start looking like glass beads. The same thing is true of an exclamation point.
If you character hits his thumb with a hammer, you can write down what he says in one of two ways:
"Ouch!" -- or -- "Ouch," he exclaimed. The punctuation mark is obviously more effective than the verb.
But NEVER do this: Ouch!!!!!!!!!!!!! Now you haven't shown pain or excitement. You've just built a picket fence, which will shut your reader off just as certainly as a real fence.
Do you even know what one looks like? Or where it came from? (Here's where my medieval training comes in handy.) An ampersand is that funny-looking symbol on the 7-key.
It originated in a medieval scriptorium, where overworked monks lettered Latin Bibles and charters by hand. Both to speed up their work and to save parchment, which was ridiculously expensive, they created symbols that worked like abbreviations. An ampersand is the Latin word "et" or "and" written with a single swipe of the pen. It's the letter "e" with the tail crossed to form the "t".
Unless you are a native speaker of Latin (in which case you are long-dead) or a monk (in which case you are just hopelessly behind the times) you have no excuse for using it. I vote to send it to the same scrap heap as the colon. Except for one example. Law firms, which tend to be old-fashioned and stuffy themselves, sometimes give themselves a name that they think looks impressive. Featherstone & Higgenbottom may have an important role to play in your novel. But writing "He bought fish & chips looks silly and sounds worse. Remember, punctuation tells an oral reader what to do with his voice. Do you really want to say "He bought fish et chips"?