KDC
I will just give some tips on all of the five tests:
RC - It was surprisingly easy this year as there were only about 1/ 1 and a half pages of material followed by 5-10 questions. Try to read the questions first before reading the text: this helps you read with a sense of purpose and saves time!
Maths - If maths is harder than English for you (like me), I suggest you do a LOT of practice. Revise the Yr 8 curriculum/crucial concepts and also the material for two years ahead! (For this year it was not really required, as it contained Yr 8 content only).
VR - Practice analogies, expose yourself to a broad range of words, and basically everything that includes puzzles with words. This was also reasonably easy this year.
NR - This was definitely the hardest for me. Master number sequences and relationships, ratio, proportion and rates, spatial reasoning etc. Know which ones to skip and do not spend long figuring out how to solve a question.
Writing (creative) - Do not think of a complex plot as this is very much time consuming and leaves you with insufficient time to finish your story. A basic plot is enough - the techniques and your style of writing is what makes it stand out.
Writing (persuasive) - Sharpen up your writing techniques (for instance rhetorical questions) and use as many as you can (for both writing pieces.) Make sure you are familiar with the structure of the writing piece. Also, it is very important to PLAN for 1-2 mins before writing the actual essay. This allows you to continuously write and finish on time. Lastly, practicing enough is essential to excel in this area (and everywhere else too!)