Haha nice to see you're so keen!

I think just going over your notes back to front and really consolidating the information required by the HHD study design is essential (Now and then, it helps to "teach" yourself by verbally reciting your notes to yourself haha although this is weird, I think it's a good way of making things stick!

) Also, don't just aim to study the textbook back to front (in fact, use your study design as your guide - no point in putting unecessary information in your notes

) - the most crucial thing for exam success is (I know it's cliched) doing questions!

Haha, do as many past questions as you can find! A lot of people (including myself at the start of last year) make mistakes of writing answers that are too long, too deviated from the question and this often snatches time from completing other questions! Aim to write detailed answers that are at the same time concise (i.e. no fancy introductions or conclusions are needed - you're writing an answer to an short/extended-answer question, not an essay question

). Also, avoid using "padding" sentences (sentences with unnecessary or barely related information) just to fill up the lines in the answering space of a question - longer answers only get marks if they incorporate related and detailed information (like examples)!
Best of luck and if you've got any Q's that need answering, get them clarified by your teacher straight away OR even better, just post it on the HHD boards here and I (or any of the other VN'ers who did HHD) can try and help out!