Here is a quick guidance of punctuation.
1. Use full-stops (/ . /) only at the end of a sentence. Begin sentences with a capital letter. Proper nouns also require capital letters.
2. Use commas (/ , /) to separate parts of a sentence to avoid any confusion with meaning. Additional information is enclosed within commas.
e.g. the pollution of rivers, which is often caused by chemical waste and fertilizer, is causing enormous problems for fishermen, especially in Britain. (The comma after ‘fishermen’ ensures that ‘especially’ connects with ‘Britain’ not ‘fishermen’.)
A comma is used after most connectives (linking words), and usually before and after a connective in mid-sentence. Commas separate clauses in most conditional sentences.
e.g. Therefore, the use of chemicals on farms should be better controlled. However, even if such laws were passed tomorrow, most rivers would take years to recover.
3. Semi-colons (/ ; /) are used to separate sub-groups within lists, but more often to join two independent clauses that are grammatically complete but closely related. However, in the latter case, you can always use a full-stop instead.
e.g. Chemical waste from factories is still drained into river systems; it is hard to believe that this practice is still allowed by law in some areas.
4. You may use a colon (/ : /) if you need to draw attention to what is to follow.
e.g. The environment is important for the following reasons:
5. Use quotation marks (/ “ ” /) for quotes and titles. Apostrophes (/ ‘ ’ /) show possession or contraction.
6. Do not use contractions (e.g. don’t, shouldn’t, can’t etc.) in formal writing. Use the full form instead. However, you may use them in the General Training Task 1, in the case of writing an informal letter.
7. Do not use exclamation marks (/ ! /) in the IELTS Writing Test, and avoid asking questions (/ ? /). However, you may use them in the General Training Task 1, in the case of writing an informal letter.
8. Brackets (/ ( ) /) are useful, especially for quoting statistics in Academic IELTS Writing Task 1, but do not overuse.