Its probably too late to make notes now so what you should do is learn all the answers to all syllabus dot points. Make sure you understand all important concepts and methods of answering questions. For biology especially, learn all the key verbs that can be asked in the question (I'll put a link at the bottom). Words like explain, assess and evaluate are used most commonly so learn how to apply the theory to this type of question. If you struggle to understand something draw diagrams which explain the concept, as a visual approach to studying is generally more effective. With chemistry answer a lot of calculation based questions, as these types of questions are generally formed around a specific structure. Make up your own questions as you study! This can help in exposing you to different scenarios. Understand all the environmental impacts and blah blah as these are ALWAYS the last, 7-8 mark questions. In these types of questions, your understanding of the key verbs becomes crucial. Finally, do plenty of trial papers (and HSC papers if you have time).