Well the technique varies from person to person. However, with Economics, its a really chancy subject, my first advice to you would be to either go to Leading Edge Tuition [It may be abit expensive, but it's worth it! I've gone there for Year 12. Start it for the 1st term and try it out!] You'll find the most useful things at Leading Edge, like past exam papers from almost every school in Sydney + extremely useful acronyms [which I will not disclose, XD since I personally know some tutors.]
Otherwise, haha you could try tutoring with Tim Riley's Tutor, which I believe is advertised in Economic resources somewhere in this sub-forum --> creative classrooms.
However, if you're a text-book type person, you'll find that using only 1 source will not be near as resourceful. In fact, its better to use at least 2 in combo, I used around 3. But Leading Edge's one is good for beginners to Economics.
Secondly, economics is not like science or chemistry where you just throw out things from your brain [Well part of it, for the Short Answers Section and Multiple Choice in the HSC/trial exams], but the big marks will be in Essays where you'll need to complete 2 out of the 4 possible choices in your HSC. Hence the reason why you need efficient ways to remember certain things, our tutor, Ankit provided us with some really interesting ways to remember what happens with Interest Rates.
E.g. SSSS --> Sexy Sally sells securities --> So my interest rate goes up.
BBBS ---> Boring Bob buys securities --> so my interest rate goes down.
That's just a hint of what you'll learn, it makes economics a really fun and interesting subject, though be prepared, once you get into topics 3 & 4, you'll find alot of repetition and crosslinking, in fact all 4 core topics that u learn in Economics will be interlinked, i.e. anything in the global economy will in some way affect the domestic economy [i.e. Australia].
Once you understand the core stuff, I'd suggest you to probably register and maybe subscribe to Economist.com, which provides you with really in-depth economic articles, mostly for Global Economy.
Well...that's the start of it. Later on I'll post up a Guide for Economics Students.