Print out syllabus dot points.
Read the dot points so you can learn actively.
Read as many textbooks as you can. Make sure you have a through understanding of the concepts.
Make DETAILED notes for the dot points. Don't worry if they are long- the longer the better. Include diagrams.
Get a write up of every prac in the syllabus. If you didn't do it get it from a friend.
Learn notes and prac. Commit every detail of it to memory.
Practice doing past paper questions. Get a teacher to mark it if possible.
Highlight the ones you get wrong and comeback to them before exams.
If you can't get certain questions because of lack of knowledge then go back to your textbook to the relavent section and add the missing parts to your notes.
Always use examples ALWAYS! Its good to know a few australian examples. D
Drawing links between modules in those long responses gets you that high band 6.
Use the padding technique in your answers. Answer the question efficiently in 1-2 lines. Then add loads of related bs at the end to show the examiner that you know your shit. If you are asked a question about enzymes draw a picture dont be lazy. Time shouldn't be a problem in biology. Impressing the marker can get you a few brownie marks
This got me a high band 6 - hope it works for you!