How to not let your English let you down

There are many common faults in punctuation which will leave a poor impression on those with a sound education in English. This applies particularly to older readers, but not exclusively. Punctuation is like dressing correctly for a job interview – do not give the other party a free invitation to reject you because you got one of the peripherals wrong! Here are some important ones:

• The colon (:) means "here comes a list" or "here is a quotation or an explanation". It is not normal now (although it used to be) to use :- as the introducer of the list. The hyphen (-) has been dropped from modern usage in this context.
• The semi-colon (;) means a partial stop, of value somewhere between a comma and a full stop (period).
• In UK English, a comma should not normally be followed by the word and; in US English the comma is required before the and in many instances.
• The comma, period, colon and semi-colon should all follow the previous word without a space, but they should of course be followed by a space. Brackets (parentheses) should have the spacing shown in this sentence, no extras.
• Quotation marks, either single or double should be used either very sparingly or not at all in a technical or factual report. They may be used to enclose a real quotation from a real person. They should not be used to enclose a colloquialism or slang unless there is simply no other way of expressing the term in proper English. If this is the case, it may still be better to use italics rather than quotation marks.
• The exclamation mark should not normally be found in serious reports.
• The question mark should always be used with a question, because it helps the reader. It would be better if we used the Spanish system and put the question mark at the front as well as the back of the question, but we don’t in proper English. It is, however, handy in informal communication such as emails.
• The apostrophe is more misunderstood than any punctuation mark in the language and can demonstrate serious ignorance.

• Apostrophes are never ever used in plurals, so 1970s not 1970’s, potatoes not potato’s, dos and don’ts not do’s and don’t’s, ABCs not ABC’s. Unfortunately the incorrect versions are very widely used and it is very difficult sometimes to be correct.
• The apostrophe is always used when there is a contraction (missing letter or letters), so does not becomes doesn’t and he is becomes he’s. Contractions like these should not normally be used in reports.
• The apostrophe also represents genitive (belongs to); Catherine’s can mean of Catherine or something belonging to Catherine, but can also be a contraction of Catherine is; the next word will tell you which it is. But it doesn’t ever mean lots of Catherines. The biggest trap here is its: without the apostrophe it is genitive and with the apostrophe it is short for it is or it has. This is an agreed convention in English, end of story.

• Know which is less and which is fewer – there were fewer flowers in my garden this year because there was less rain - is correct. Fewer is used with numbers, less with something that cannot be rendered as a number.
• That or which? Here is a useful example: There are several types of language convention that could be used; the best, in UK English, which, after all, is what we are trying to use, is to use which after a comma, which immediately throws an emphasis on the particular topic in the phrase before the comma; otherwise it is a much more general approach that is indicated.
• The following is an extract from the relevant section of 'Mind the Gaffe', by R.L.Trask (Penguin): that, which, who.  A relative clause may often be introduced either with 'that' or with 'which' (for things) or 'who' (for people).  So, you may write either 'the topic that I want to consider' or 'the topic which I want to consider' (or, in a more informal style, 'the topic I want to consider').  However, it is impossible to use 'that' if the relative clause is non-restrictive - that is, if it does not serve to identify the thing under consideration, but only serves to provide more information about that thing.  So, you must write 'the Suez Canal, which was opened in 1869', and you cannot write 'the Suez Canal, that was opened in 1869'.

• Always read your own work before sending it. This applies to emails as well.
• Clear writing first time can save so much extra work later.