Our general rule is to avoid brackets as much as you can, but here's some advice when they have forced you into a corner.
Use these when you need to expand on or clarify something:
It reached a length of 2.3m (7.5ft).
Or when you're using an acronym or an initialism for the first time:
The decision was made by the University Executive Board (UEB).
Otherwise, look for alternatives. For example, in sentences with parenthetical statements – like this one – dashes look much better:
The Hypsilophodon – a small dinosaur from the Early Cretaceous – was omnivorous.
When it comes to using punctuation in brackets, include it before the closing bracket if the complete sentence is in brackets.
<aside> ✅ I arrived at work at 9.30am. (That’s earlier than usual.)
</aside>
Otherwise, punctuate after the closing bracket.
<aside> ✅ I arrived at work at 9.30am (which is earlier than usual).
</aside>
But again, we'd prefer if you got rid of the brackets altogether. Funnily enough, a dash looks better here, too:
I arrived at work at 9.30am – which is earlier than usual.
Like their round cousins, try to steer clear of these. Only use them for comments, corrections, references or translations made by a subsequent author or editor: