Here are some simple rules to help you with punctuation for IELTS writing:
Full stops are very important. Put a clear full stop at the end of each sentence, and then begin the next sentence with a capital letter. If you don't do this, you will get a low score.
- When you start a sentence with these words, put a comma after them:
Nowadays, Recently, Firstly, Secondly, Finally, Furthermore, In addition, Also, However, By contrast, On the other hand, In my opinion,...
- We use commas in lists:
e.g. This problem affects individuals, communities and society in general.
- We don't usually put a comma after the word "that":
e.g. It is clear that the rate of immigration increased.
- Don't worry about other uses of commas. The use of a comma is often optional in other situations.
Avoid contractions in IELTS writing. Use "do not" instead of "don't".
You may sometimes need to show possession e.g. the government's decision.
You don't really need to use any other punctuation in IELTS writing.
My advice is to avoid trying to use colons and semicolons.