It's pretty simple: good writing relies on correct punctuation. No matter how beautifully worded that story, how intelligent that essay, how persuasive and informative that report - if your punctuation is all over the shop, chances are no one will ever bother to read past the first line. In my work as a proofreader and copy editor I come across all manner of punctuation problems. Below are the most common mistakes I find time and time again.

Full stop: Okay, okay, it's pretty obvious, but every sentence needs a full stop at the end. You'd be amazed how many people miss this.

Quotation marks: Whether you're using double quotation marks ("") or single (''), ensure that each time you use an opening mark, you also use a closing one.

Apostrophe: Please check this is facing the right way (remember, it looks like a 9) and that you use an apostrophe in words like can't and won't, as your spellchecker won't highlight these as errors.

Exclamation marks: Used at the end of a sentence, there is no need to follow an exclamation mark with a full stop (or indeed another one/two/three more exclamation marks). 'Suddenly, there was a crash!'

Question mark: As with the exclamation mark, the question mark is never followed by a full stop when used at the end of a sentence. 'Where is the bus stop?'

Overdoing it: Overuse of punctuation is a marker of weak writing. Consider the difference between 'Bang! The man fell to the ground, dead.' and 'Bang!!!! The man fell to the ground!!!! ... Dead!!!!!' By all means use the full stop liberally, and the comma where necessary. But if your work is peppered with exclamation marks (especially multiple ones), question marks, dashes, colons, brackets or ellipses (. . .), go back and see if you can simplify some sentences.

Underdoing it: Having warned of the perils of overusing punctuation, there is also the opposite problem to address: lack of punctuation. The easiest way to check whether your writing is missing punctuation is to read it aloud - punctuation is needed where you pause as you read, so if you are going blue and gasping, chances are you could do with some more punctuation.