There are thousands of rules about punctuation. This section attempts to cover some basics.
accents (This also appears in Grammar): A thorny topic. Some feel that French words should have the correct accents. I don’t, providing the meaning is clear. One word where an accent may be necessary is divorcé (the masculine of divorcée, to distinguish from the word divorce). You can get away with divorcee, fiance and fiancee on the grounds that unlike divorcé, they do not have alternative meanings without the accent. Some authorities say that divorcee is fine for both male and female, like payee or addressee. I think you should stick to masculine and feminine versions because they come direct from the French, whereas employee, for example, is the partner word of employer, a different construction altogether. However I don't care for either divorcé or divorcee for a man, and you can easily write ‘Mr Smith, who is divorced . . .’ I have seen a reader’s complaint about the absence of an acute accent on coupe, as in car, which he thought could be confused with coupe, meaning a dessert of fruit and ice cream. Both these words are French in origin, but I defy anyone to come up with a sentence in which a car could possibly take the place of a pudding. The same reader felt that it was wrong not to put accents on ‘menage a trois’. Again, this cannot be confused with anything else. In any case, there never seems to be any suggestion of using accents on Spanish, German or Scandinavian words, so really I cannot see a logical reason for treating French differently.
ampersands: Use only when they are part of a company name, eg P&O, Marks & Spencer (note individual spacing formats and see spaces section below). Never use them in such a context as ‘bacon & eggs’.
apostrophe (1): You don’t need one in ‘six months pregnant’ because the time period is acting as a modifier of the adjective ‘pregnant’. However you do need one in ‘he was sentenced to two years’ jail’ (though ‘he was jailed for two years’ is more elegant as well as shorter) or ‘six months’ time’ because the time period is acting as a modifier of the noun ‘jail’ or ‘time’. You can test whether you need one by trying out the singular such as ‘one day’s time’ or ‘one month’s pregnant’.
apostrophe (2): ‘plural’ names, such as Jones or Wales: Mr Jones’s house; Mr and Mrs Jones’s house; the Jones family; the Joneses went on holiday; the Joneses’ house. This last looks pretty clumsy so usually you would find a way round it, such as ‘the family’s house’. Note that a ‘plural’ name is not treated the same as a plural noun in terms of apostrophes. It is incorrect to say ‘Mr Jones’ house’ or ‘Prince Charles’ list of engagements’. The latter should be 'Prince Charles's list of engagements'.
apostrophe (3): plural nouns that do not end in ‘s’, such as children, take an apostrophe and s, thus: children’s home, old people’s home (by the way please don’t put ‘children’s playground’ unless it is to distinguish from an adults’ playground.)
apostrophe (4): it’s/its: it’s is a shortened form of it is or it has, for example ‘it’s a big task compiling this style book and it’s taken me a long time’. Its is the possessive of ‘it’, in line with the other possessive pronouns mine, his, hers, theirs, ours, yours, whose. These incorporate the idea of possession so they do not require an apostrophe. So ‘the cat sat on its mat’. There is no excuse for getting this wrong.
apostrophe (5): couples: If two people own the same item, the apostrophe and ‘s’ go after the second name only. If two people each own an item, both have an apostrophe and ‘s’. So: ‘Jack and Jill’s house’, but ‘Jack’s and Jill’s cars’.
apostrophe (6): Occasionally an apostrophe is needed for clarity, for example ‘dotting the i’s and crossing the t’s’ (you could get away without one in t’s, but be consistent within a sentence). You do not need an apostrophe in dates such as 1920s.
brackets: If you are using brackets to explain something within a sentence, such as ‘We do not often use parentheses (round brackets), but occasionally they are necessary’, the punctuation is outside the brackets. If a whole sentence is contained in brackets, the punctuation is inside the brackets.
Square brackets are used to insert a word which was not said by the speaker but is necessary to make the quote clear, eg ‘Mr Brown said that he was an idiot’ could be ‘Mr Brown said that [Tony Blair] was an idiot’.
colon: Apart from introducing quotes or lists, use sparingly. They are fine in literature but can seem a little pompous in newspaper copy. The correct use is to connect two parts of a sentence where the second expands on or explains the first, such as ‘He had many hobbies: trainspotting and stamp collecting were his favourites’. In headings, a colon should be followed by a cap, as in ‘Cameron: This style book is brilliant’, but in copy lower case almost always looks better.
comma: Overused, but vital. You do not need one after ‘Yesterday’ or ‘Last night’ at the beginning of a sentence. If you are using commas to separate out a part of a sentence, they must be in pairs, as in ‘The meat, which was bought last week, was beginning to smell’.
If you are describing one individual, you would need commas in a sentence such as ‘The Queen, who visited Canterbury yesterday, was greeted by . . .’ However if you are describing one of several individuals, you should not use commas, eg ‘the sub-editor who changed that copy is a genius’. Commas are occasionally needed to make a meaning clear, as in ‘I would like to thank my parents, the Queen, and Prince Philip’. If you miss out a comma, you get ‘I would like to thank my parents, the Queen and Prince Philip’, which is not quite the same thing. Another example given when an American academic suggested that the comma was redundant was ‘Mrs Smith gets pleasure from eating her family and pets.’
A comma should be used to separate two adjectives if the word ‘and’ could be inserted between them. For example, ‘He is a tall and handsome man’ could be written as ‘He is a tall, handsome man’, but you could not use ‘and’ in ‘the gifted American singer’, so you do not need a comma.
In a list, put commas after every item except the penultimate one which is followed by ‘and’. For example: ‘They bought bread, butter, sugar and tea’.
You should not use a comma after an exclamation mark or a question mark, but an awkward case is Which? Magazine. For clarity it is occasionally necessary to use a comma.
contractions such as shouldn’t, won’t: These should be avoided in copy on serious topics because they have too ‘chatty’ a feel. They are fine in quotes or in light-hearted pieces, and may be acceptable in headlines.
dash: Use sparingly. They hold up the sentence and make the copy look ‘spotty’. In most cases they can be replaced by commas, or even deleted. They should be used only for a surprising twist to a sentence, such as ‘Jason Bugby is three months old – but he is already a member of Mensa’, or to enclose something which does not fit into the main subject matter of the sentence, such as ‘Despite spending so much time abroad – last year he was in England for only two months – Lord Freeman maintains a fully staffed house in Hertfordshire’. Incidentally, dashes are longer than hyphens, usually on the shift of the hyphen key, and need a space at each side.
ellipses: In copy, ellipses (three dots) should have a full space (space bar) at each end and a thin space (which you should be able to find somewhere on your system) between each dot. They should appear thus . . . not thus ... or thus... Ellipses should be avoided like the plague to fill out a line in a heading. The correct use of ellipses is to indicate that some matter, usually in a quotation, has been omitted, or that more could be said, eg ‘But that’s another story . . .’
exclamation mark: Occasionally ok in headings, almost never in copy, even in quotes. It replaces a full stop or comma, so should not be followed by either.
full stop: Using these after initials in a name such as A. A. Gill can look ‘spotty’ and many favour dropping them (though, apparently, the point is part of P. Diddy’s name). I think you should put A A Gill, with a half space between the initials and the surname. Use a full stop rather than a question mark after an indirect question, eg ‘He asked which way to go’. You should not use a full point after an exclamation mark or a question mark.
hyphen: If you are putting two or more words together to make an adjective in front of a noun or name, you would usually hyphenate it. Thus: ‘Father-of-three James Cornish said . . .’ If the words follow the noun or name, they would not usually be hyphenated. Thus: ‘James Cornish, a father of three, said . . .’ Hyphens can be used to attach prefixes such as over, under, inter and multi, but not always. Basically use a hyphen if it would look peculiar without one (such as reinterview) or have an ambiguous meaning (such as recover and re-cover), or where a vowel would be repeated, such as re-examine, co-operate. Otherwise run the prefix and the word together, as in ‘multipurpose’ or ‘bilingual’. Hyphens can be used to make two words into a third with a distinct meaning, eg ‘ball-boy’, but sadly this is far from consistent and many compound words that would seem to need hyphens remain two words, such as ‘guinea pig’, ‘time bomb’ and ‘ice cream’. If in doubt, use a dictionary.
You do not need to hyphenate adverbial compounds where the adverb ends in ‘-ly’, such as ‘the stylishly dressed man’. Use a hyphen only when the adverb does not end in ‘-ly’, such as ‘the well-dressed man.’ When the same form of words appears after the noun, do not hyphenate, as in ‘the man was well dressed’. Hyphenate all spelled-out fractions, such as ‘three-quarters of an inch’.
inverted commas: Some papers such as the Daily Mail use single quotes, with double quotes within if necessary. Other papers have the reverse style. I would go for single because it looks neater. If you are quoting a full sentence, end it with a full stop then an inverted comma. If it is part of a sentence, finish with the inverted comma, then the full stop. So: He said: ‘I fancy a beer after reading this style book.’ And: He said that after reading the style book he could ‘murder a beer’. The same applies if a comma is involved instead of a full point. So: 'I am going to read the whole thing again,' he said. Try to keep the use of inverted commas to a minimum as they tend to make the copy just that bit harder to read. For example: He said it was a ‘cynical’ device. You have made it clear that it is someone’s opinion so you don’t need inverted commas on ‘cynical’. If you are using quotes within quotes, introduce the double quotes with a comma, not a colon. So: She said: ‘I was hanging out the washing when a man ran up and said, “There’s been an accident”.’ Close the double quotes, put the full stop, then close the single quotes.
question mark: A feeling seems to have evolved in some quarters, such as the Daily Mail features department, that these are optional. This is an entirely wrong feeling. If it is a question, it needs a question mark. No argument. The only time you do not need one is when the question is indirect, such as ‘He asked if she would go out with him’. An awkward construction sometimes arises in subdecks which include a byline such as ‘Do aliens really live here, asks Judy Bywater’. The question mark looks wrong wherever you put it. ‘Do aliens really live here? asks Judy Bywater’ is technically correct but clumsy, while ‘Do aliens really live here, asks Judy Bywater?’ is obviously incorrect. I think the best way round this is ‘Judy Bywater asks: Do aliens really live here?’ Like exclamation marks, question marks should not be followed by a comma or a full stop, but the annoyingly named Which? magazine occasionally needs a comma for clarity, eg ‘Various magazines, such as Which?, exist to inform consumers.’ Again, I would try to rewrite the sentence, perhaps to ‘Which? and various other magazines exist to inform consumers.’
semi-colon: A perfectly good punctuation mark which is not so much used in newspapers. Its role is to connect two parts of a sentence where a conjunction is omitted, such as ‘The cat sat on the mat; the mice watched from behind the sofa’. For journalists, it is mainly used in longer lists. If the last item in the list begins with ‘and’, it should be preceded by a comma, not a semi-colon.
spaces: Initials and names such as W H Smith and A A Gill should be separated by thin spaces (not like these, which are full spaces, but I can't find out how to do a thin space on my computer). The financial firm J P Morgan is inconsistent on its own website about spacing, so I suggest doing it the standard way. It’s a fiddly business but looks so much better.