Punctuation, or You really have to see Victor Borge do it

I like using punctuation marks. I try to use all of them. The thing is that there aren't many real punctuation marks--you can ignore the apostrophe as a punctuation mark for instance (I think of it as a kind of letter) which leaves fewer than ten to deal with. You could make your life more complicated with punctuation marks (the British poet, W. H. Auden said that he never understood punctuation) but you can also make some simplifying assumptions to eliminate most of your difficulties.

There are the three that go at the end of the sentence: period, exclamation mark, question mark. You should never use the exclamation mark (I tell authors whose articles I edit that they get one exclamation mark per article: use it wisely). If something isn't important to the reader, putting the band (!) at the end of the sentence won't make it important (nor will putting "Note that" at the front). If something is important tell the reader why it's important or tie it to something that's important to the reader. I only use the exclamation mark to indicate that I--the author--am surprised by something. So really, you only have to determine if your sentence is or isn't a question to determine if you end with a period (full stop in the UK) or a question mark.

Writers tend to have more trouble with the six punctuation marks that go inside sentences: the comma, the colon, the semi-colon, parentheses, quotation marks, and the em-dash (the dash that's about the width of the letter "m" in whatever font you're using).

Some are easy to handle. You can go your whole life without using the semi-colon, for instance. It's there when you want to jam two sentences together into one sentence. In that situation, of course, there's no reason why you can't just have two sentences separated by a period. But, if the two sentences are tightly related, you have the option of joining them with a semi-colon. Some style guides will have you capitalize the first letter after the semi-colon; some will not.

The quotation marks ("" or '') are easy to handle, assuming you need them at all because they always come in pairs and are used exclusively to enclose words taken literally from some other source. Parentheses have the same kind of regularity in that they are always used in pairs. You should use them to mark out material that could be left out of the sentence entirely (like this phrase).

Colons have at least two uses: To introduce a list and to signal a definition or explanation. The previous example used the colon to introduce a list. But the second purpose is more rare: It hardly happens at all anymore. So, again, you could use the colon exclusively for introducing a list and make your life considerably easier.

It's the comma that causes the most grief, I think. Part of the problem is that it, like the colon, has two separate uses: To separate items in a list and to mark out phrases in a sentence. When used to separate items in a list, you run into the issue of the serial or Oxford comma: do you have a comma before the "and" at the end of the list ("apples, bananas, and oranges") or do you omit it ("apples, bananas and oranges"). I'm a serial comma kind of guy myself but, really, it's a style guide issue: make a decision as to whether or not you use it and move on with your life.

Other than that, commas are used to mark out phrases. If the phrase appears at the start of the sentence then you need only one comma at the end of the phrase. I like to use that comma but, as the world moves to a more open punctuation style, it's becoming optional. Here again, if you want, you can omit that comma.

Commas are also used within sentences to mark out phrases, in which case (like parentheses) they always come in pairs: one at the start of the phrase and one at the end  of the phrase. You can test to see if your commas are in the right place by removing everything between the commas. If you can't find the closing comma you should add it; if the sentence that's left makes no sense then you've put your commas in the wrong place and will need to move the beginning or ending comma. Like parentheses, the phrase inside the commas should be a "less important" part of the sentence.

You could make your punctuation more complicated but why? And if you do get frustrated, you can watch Victor Borge handle it better than anyone else.

Reading or read
The Cello Suites: J. S. Bach, Pablo Casals, and the Search for a Baroque Masterpiece by Eric Siblin
30,000 Years of Art: The Story of Human Creativity Across Time and Space by Editors of Phaidon
You Know Me Al by Ring Lardner