well for continuers i went through the whole year knowing the syllabus and everything, and didn't do that much revision before exams and basically relied on what i knew. i was always really relaxed, and basically.. relying simply on your knowledge takes you a long way. but being thoroughly prepared will take you further. i was confident about the course but only got mid band6, i'm sure if you took the extra time to find more sophisticated ways to say things, or have more complex sentence structures, a high band6 would be more achievable.
and for extension. be prepared for the speaking. the questions don't end up looking as daunting on the day. but yeah, make sure you do heaps of practise starting from months beforehand.. and i would definitely encourage memorising some good sentences to use early on, so that it's readily accessible when your mind is in a twist on the exam day. remember that speaking is in august or something early on like that.
and the writing component.. the first bit where you read an extract from the set text.. it's BULLSHIT BULLSHIT BULLSHIT. if you do alright in english, then it's a piece of cake. and for the other sections - prepare for them as much as you can by practising complex sentence structures etc.
i screwed up the speaking by quite a bit (the exam was on the saturday after my trials had finished.. i finished my notes at 4am and didn't know half of it) but ended up with 47/50 which isn't too bad. so yeah, don't be too worried if you screw up a bit here and there, but always be mindful about it, and try to compensate for it later on.