One thing that helped me: the notes from the marking centre. These can be found on the Board of Studies website for each exam, and they give advice on what was needed for each question.
Sometimes it's really surprising what they require you to include in your answers, but after you've done enough practice and looked through the notes enough, you will be able to pick up trends - this is super important as a guide to structuring your answers in exams.
But generally:
* know your syllabus, and the words of the syllabus - use BoS phraseology wherever you can
* always remember SI units, state symbols, etc
* don't go too far over the lines - you risk contradicting yourself and losing heaps of marks
* be structured and concise in your answers - use dot points! I never wrote in paragraphs, even for the 5+ mark questions
* answer ALL PARTS of the question, pay attention to every word of the question
* use tables for comparisons, labelled diagrams when appropriate, and chemical equations whenever you can
Develop scaffolds for answering questions of the different verb types (especially evaluate, assess, discuss, etc), and practice them a lot. When you get to these questions in the exam you will have answer structures that you can utilise when answering the question.
For example, for a discuss, your scaffold might be:
Definition: _________________________
__________________________________
Concluding Statement: ____________
_______________________________
I found this really helpful!