Hmm ... did it last year
Dunno how much time you've got left... But you can learn a HELL of a lot in a few days
I had a million questions written out for each topic, and about a paragraph answer for each... Prepare your sentences using as many of the senior structures as you possibly can (SERIOUSLY JAM THEM IN THERE), whilst still keeping it natural. I practised these so many times that i had answers flying about my head all day n night haha. Whether you should do this really depends where you're at and what course you're doing. (i was doing continuers?)
I remember when i started the hsc course, my goal was to be relatively fluent by the end of the year. Didn't quite happen... But my speaking went very well, especially in the trial (20/20). Memorising isn't the best way to communicate, but when it comes to learning a language like japanese, it's all about getting the various sentence structures rolling off your tongue smoothly. (Like, EVERY structure in the textbook). Then you can apply any vocabulary to the basic sentence outline and you have yourself some great answers.
Also, you should have a search for SAMPLE speaking HSC answers. Can't remember if it was on Board of Studies or not, but the sample for band 5/6 was really good and sort of gave me confidence too, because the guy was obviously fluent, but he made mistakes with vocab and his answers weren't learnt ... A reoccuring thing I noticed was that no matter how fluent you think you are at a language, in the end it comes down to showing off the structures and vocab IN THE HSC COURSE and doing so as naturally as possible. So even though a girl in my class had lived in Japan for a year and was fluent, she was pretty cocky about it and so made her answers up on the spot and failed to use a good proportion of the HSC structures... And so even though she was way better than me at Jap, i beat her =]
Yeah so just practise practise practise... Learn it like a speech.
OHHHH and have prac runs with your teacher and anyone good in your class... Just to get practise at those unexpected questions or altering your prepared answers on teh spot.
OMG i miss Jap... *tear*
