Im in a class of 2 however my school cross marks so I'm up against people i don't know. My advice is to make up a Vocab sheet asap then go through all past exams, get the generic questions of VCAA make a formula for example the image evokes a sense of happiness and warmth + this is reinforced the (design element/principle) + describe the design element and the characteristic of it. I did Vis Com in year 11 and since then I've forgotten the difference between formal elements and design elements. But without this formula I tend to waffle and waste to much time in the exam. Also I tend to wonder into the Vis com class occasionally 
Hehe, I have all the elements and principles in my head. Heres an example of a question that throws me off:
Identify and describe one dominant design element and discuss how it has been used effectively in this
design.
http://i.imgur.com/I4UkD3R.pngVCAA: Letterform has been used in the Small World designs effectively in an illustrative manner, stating the name of the business. Each
letter has been drawn in the shape of an article of clothing i.e. socks, or overalls, or pants…etc. The variety of usual shapes of
children’s clothing which create the business name. This is effective in catching the audience’s attention
as they are unusual. 
This also helps to communicate what the shop sells through the letterform design.
I might be too cynical but this answer seems pretty senseless.