So I've said this in every thread I've replied to so far, but in terms of text books, I swear by Riley. I personally find the Dixon book (which your school probs uses) good for a basic summary but for essays, Riley's content is in-depth with plenty of stats.
That's the other thing - economics markers love a good stat and graph. Make sure they are up to date, though; I've been flamed a few times for citing policies from the 70s...
Make summaries
during the term because it is obviously a content-heavy course. My prelim teacher made me do summaries and would check them, and I still do it with my new teacher because it does work.
Keep up to date with current economics news. Read the papers/news, if you can convince your parents to get an Economist subscription that'll prove incredibly valuable. Not necessarily required though
The syllabus for eco in terms of essays is usually pretty narrow, which means you can write essays in the month or so before the exam and pretty much cover everything.
I'm happy to help if you have any eco questions - shoot me a message.
Edit: Here's a link to Riley's book
http://timriley.com.au/website/ - I realise not everyone shares my platonic love for him and might not know the name of the book.