If you review a document, it means you read it and examine it (and maybe have some ideas to improve it) - but you don't make any changes.
If you revise a document, it means you change the text to correct errors or make improvements.
When preparing for a test, it's a good idea to study the material again in order to refresh your memory. American English speakers say you are reviewing for the test. British English speakers say you are revising for the test.
Stay attentive to the ideas put forward by other group members and keep writing the important points discussed during the GD As you get a chance to speak, put forward your views about the topic. You can also agree or disagree with other?s ideas, based on your knowledge about the subject.