Most errors can easily be cured by keeping a calm head, not rushing and reading the whole question.
Unfortuantley its just so hard to do this in an exam.
You see something unfamiliar you panic. Or perhaps see something familiar, jump to conclusions and fail to read the rest of the question; the momentum graph on this years physics is a perfect example.
Atleast this is what happened with me this year. Physics i did not care much about prior to exam, i do not enjoy it and frankly hate it lol. So in the exam room i was relaxed and couldnt really care about the outcome; that isnt to say i didnt try hard, but i was really relaxed, and as a result did quite well (i think)
In contrast, i made so many silly and preventable errors in chemistry. Rushed through the whole thing, finished with ~30 minutes to go; and fell for most of the 'tricks' VCAA threw at us. And i put this down to the fact i wanted to do really well at chem. I'd done so much study, and knew everything so well. Had done well in all my practice exams, but i had just put way too much pressure on myself to do well.
moral of the story. take it easy lol.