Best exam practice is VCAA exams and very carefully reading the assessors' reports. Trial papers are not that great and some are just reworked VCAA papers of the previous year. Know your work. There is a limit as to how much practice exams will improve your marks.
Exam techniques is also very important. Use the reading time to first determine which questions you find the easiest, then plan your strategies for the more difficult questions, and lastly, start doing some of the questions in your head. This will save time during the exam. When you are allowed to write, do the questions you find easiest, then go back to do the more challenging ones.
At all times, keep your head. If you come across a question you can't do, don't waste too much time staring at it - get all the other questions done checking there are no silly errors.
If you are unable to do a "show that" question, use the given answer for the following questions.
Don't leave out any multiple choice questions - guess if need be.
Your teacher should be giving the same advice. Remember to use your teachers throughout the year for help. Don't allow too much time to pass between not understanding a concept and seeing your teacher. If your teacher is unavailable, ask to see another.
Good luck. Hope you enjoy the subject.