Some great tips here on CASA exams!
I am an Avionics LAME, and completed all the CASA exams for this trade years ago, and well before you went to a training college and did them through a course.
All of mine were done through home study, and out of 20+ exams, I failed a few before I realised that in a lot of instances I was failing to do what John above has said:
RTFQ thoroughly.
Discount that which is obviously incorrect, then make a case for the remainder as to why they may be right.
RTFQ thoroughly
Practice exams should be viewed as a guide to the style of questions and to the subject matter that may be examined, NOT the specific answers to questions.
Here's a tip also: If you print out and use the Day VFR Syllabus with the practise exams and exercises, make sure you haven't printed it "fit to page". Otherwise you will be confused as to why you are getting all the navigation calculation ones wrong. The Sydney, Bourke and Townsville WAC's will be the wrong scale
Cheers!