The EXCEL Economics books are brilliant, IMHO. Also the Leading Edge text books are quite informative. The Leading Edge website comes in handy for news updates and answers to the multiple choice/short answer/essay questions in the question book that is associated with the main Leading Edge textbook.
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Just serious and constant revision will get you through. It's all about linking information and terms so make sure you revise what you've learnt, so you can keep up later in the course! Make sure you get this down pat in Year 11, as your Prelim year acts as a necessary base to the things you be learning in the HSC.
Having a background knowledge on current affairs is always handy, as you're able to refer to present events when re-presenting things you have learnt. It helps with context too and having knowing what is happening in the news, you may be able to write about it in an essay to show your understanding. Plus is may assist you in grasping a concept.