So: round brackets, properly known as parentheses. What are they used for?
* to offer the reader an aside (which is a thoughtful thing to do);
* to give an unimportant piece of information (in which only a few readers may be interested);
* to offer extra information (such as a fuller explanation of a term or unusual word);
* to enclose an afterthought or observation which is witty (or not so witty!);
* to provide an example (such as this!);
* to enclose alternative terms (ie expressions or names);
* to point out there are other options (or choices);
* to give a translation of a foreign mot (word).
There are many others, of course, such as to contain birth and death dates of a named individual, and to enclose an acronym of a body you’ve just mentioned.
So far, so good. The mistakes, when they come, usually concern punctuation. To avoid most of them, there is a golden rule: the article and every sentence in which your parentheses are contained should remain punctuated correctly were you to remove the parentheses and their contents.
Here’s an example:
This is a sentence, (which contains fourteen words), but it is punctuated badly.
Remove the brackets and their contents and you’re left with:
This is a sentence, , but it is punctuated badly.
Yes it is. You need to lose one of those commas, and although it may seem counter-intuitive, in such an instance it should be the first of the two to get the chop:
This is a sentence (which contains fourteen words), and it is punctuated correctly.
Repeating the bracket-removal job:
This is a sentence, and it is punctuated correctly.
Which is fine. Arguably, you could lose the other comma as well.
Here’s one with brackets at the end of a sentence:
This is another example (an important one!).
Many writers would not insert that final full stop, but you do need it, because without it, and without the brackets and its contents, you’d have an unpunctuated sentence.
If it’s a whole sentence, keep punctuation inside:
(This is another important example.)
And if you were to remove that, then the article would remain punctuated correctly, because you’ve merely lost a whole line. And that’s the golden rule in action again.
As for usage and style… well, some writers use brackets frequently and some hardly ever. Some are snobby about them, feeling them unnecessary and affected, but there are brilliant writers who love them (the journalist Zoe Williams, for instance).
If you find yourself using lots, perhaps consider rewriting a few sentences in such a way that you no longer need them.
If you can, avoid them in the first and second paragraphs when you’re establishing the article and you shouldn’t be distracting the reader with subsidiary information.
Don’t later refer to something you previously only referred to in parentheses (unless, of course, the reference is again in parentheses). (The only counter-example I can think of is when you refer to an organisation with a long unwieldy name, offer an acronym within brackets, and in later references use the acronym. Let me know if you can think of others.)
Essentially, your sentences and your article should not be ‘aware’ of what you put between brackets; they should stand independently of them.
I think that’s it. (Sorry, much longer than originally intended.) (And far too many brackets too.)