Essentially, it would be a good idea to revise the content of a subject to ensure that you have a thorough knowledge and understanding of the content, allowing you to then complete past exam papers and effectively apply your knowledge of the content to exam questions. As you complete more past papers, you can then identify areas of improvement and address them by going back to the content and completing additional past papers.
In terms of the specific aspects of assessing your performance in past papers, the marking guidelines can help, especially since they set the expected standards regarding response depth and focus. You can also use the syllabus of the subject to ensure that you discuss the correct concepts in your response, and subsequently use your notes and/or your textbook to make sure that you have discussed the particular concepts accurately. This is applicable to Business Studies, where there is a heavy focus on the syllabus, and this is reflected in Section III and Section IV in that you must correctly identify and discuss concepts to maximise your marks.
Receiving feedback from your teachers is a good way of assessing your progress as you continue to prepare for your HSC exams. You can definitely request feedback from your teacher targeting your Section III and Section IV responses, as well as for subjects like English, where teacher feedback can greatly assist with improving the quality of your writing. This is something I personally did with English Standard back when I did my HSC, and have made sure that my younger sister, who is taking English Advanced and starting year 12 soon, does as well.
You can also post threads on BoS, as other users may be happy to provide you with useful feedback.
I hope this helps!