Hey, I got in through Year 10 entry but did minimal preparation for the actual test, mainly for the JMSS one which really helped
. Make sure you don't put all your effort into test preperation, because the truth is that they are looking for all-rounded students that do extra-curricular activities outside of school, such as sport, music and drama.
For Academics however:
Maths - Make sure you understand everything in the Year 9 textbook, and do exercises correlated to examples so that you know you are on the right track. I recommend Cambridge Essentials for a textbook
Numerical Reasoning - Do practise papers, I'm sure you can find multiple on the web. Maybe purchase a patterns book and work your way through that, because there are plenty of questions that ask you to identify a pattern
Reading Comprehension - Read as much as possible! You have over half a year to prepare from now so make sure you can read really quickly and absorb the information at the same time.
Verbal Reasoning - Again, read as much as possible so you can pick up vocabulary
Persuasive Writing - Write practise essays, and try and get used to a certain structure (Work out what is best for you, I use Intro, 3 Body Paragraphs with a main point in each, and a Conclusion)
Creative Writing - Similar to persuasive writing, but you can't really prepare a structure. This is where learning sophisticated vocabulary can really come in handy, if you can recall upon them in the right context, you will receive glowing marks
I highly recommend joining a sporting club outside of school now, not only so you can include it in your application, but also for the health benefits and fun
. Get involved in everything you can find happening around your school, such as drama productions, leadership roles and volunteering. They are looking for all-rounded people, don't forget! Make sure you work on your speaking skills for the interview, some people are naturally good at them, but many people find themselves shy in high-stake interviews.
Good luck, and sorry for the lengthy post!