I thought doing Methods in its entirety during the hols really helped me to understand the concepts very clearly before term started, so that when I was in class, I would not have to focus on learning the basics, but rather gaining valuable knowledge of the nuances of each topic.
Also, I was able to try past papers (I did about five VCAA and a couple of company ones - I only marked the VCAA ones), which was really important for me to test my knowledge.
I reckon sciences and maths are good to do in the hols (I did most of Unit 1 physics and quite a bit of chem - lots of stoich).
For languages, it's probably better to just go through the grammar and vocab and learn them solidly.
Obviously, I did not do any prep for Cisco

as that would have been completely pointless
I hope this helps!
