Oh, you're doing the IPT/IT/SSD combo. As passionate as I am about computing and its applications (especially network engineering), I would have committed suicide if I stuck with the initial 6 unit IPT, Industrial Tech: Multimedia and IT combo that I studied during prelim, haha. =P
To study for 2U, I made summaries based upon the content of my reference notes from school and the Excel HSC Mathematics textbook by Lyn Baker. I preferred the layout of the older Lyn Baker publication to the newer one in the fancy blue cover, but the content is essentially the same. Following production of the aforesaid summaries, I would do practice questions from the Excel textbook. After mastering the practice questions, I would move onto the Excel Success One past papers book, doing past HSC questions relative to the topic I was studying, or whole papers leading up to the HSC.
My mark for the HSC examination was 93, however, I slacked off during the half yearlies and topic tests, giving me a ranking that was below my potential (12/40-something), so my assessment mark was only 84. Hell, I could have even done better in the HSC if I wasn't watching Lost most of the time I was meant to be studying. Just make sure you don't slack off leading up to the school exams like I did, haha.