Honestly, I could give the same advice I used for Advanced, which is just to practice heaps and most importantly, GET WRITTEN FEEDBACK. Even if you can complete 1 or 2 practice essays a week and ramp it up before exams, this will have give you plenty of practice writing essays to different questions and completing them within the time limit. If possible, get a tutor (although I understand it can be quite expensive and may be infeasible) to give you feedback; if that isn't possible, then asking your teacher for feedback can also be very beneficial.
Also know your texts very thoroughly (don't just read it once or not even read it at all); revise them a few times throughout the year, as you will be bound to forget certain bits of information and have clear notes based on ideas, characters, etc (however you feel comfortable with doing so).