There was a similar question on the chemistry forum so this is basically a copy and paste of my answer there:
First write out really comprehensive notes that are well aligned with the syllabus. This is mostly just to make sure everything is covered and there are no little gaps in your knowledge that could surprise you in the HSC or any assessments along the way (I'm guessing this is what you've already done, right?). Then move on to past paper questions. Reading over your notes is a pretty passive way to study and doesn't really do much for your retention of knowledge. Applying what you've written in your notes to questions is the best way to go.
What I would always do was take a HSC question, answer it first off the top of my head, a second time after having re-read that section of my notes and a third time after checking the HSC marking criteria and sample answer. Doing a marathon with friends where you put each other on the spot with past HSC questions or syllabus dot points is another great way to study (though good luck rounding up willing participants in the holidays haha). Give your notes a quick skim the night before an assessment, but other than that past paper questions are absolutely what you should be doing as soon as your notes are finished.
Another good thing to do is to take your notes and just condense them over and over again. Refining them right down until you have just the really important information. First take all of your notes for say nuclear chemistry and try to refine them down into two pages, then get them down to a page, then just ten dot points of the most important information. That way when you have an upcoming assessment you can just read those dot points before you go in to make sure all of the most important information is in your head. It's also a way of reading over your notes that's a bit more active, because you're selecting the most vital information rather than just sitting there reading. That way you retain what's in your notes better, because your brain is working harder than it would be if you were just reading them.