+1Don't study hard. Study smart. This is an advice from my teacher.
There's no point in continually going over all your notes or spending too much time studying if you don't understand it, don't know the skills or if they're not going to be tested anyway.
Go over past papers and see what they test you in. Don't waste your time on studying every single thing the teachers give you -- especially Science because from what I can see only some of the questions are based on knowledge.
The rest are skills so you better practice on that more than studying (though there are some skills there that require at least a bit of background knowledge so don't completely abandon studying either).
Summaries are <3. Go into details later on once you're sure you know the basic gist of it and if you have enough time. This is useful for cramming because once you get the basic idea of it, if you didn't have enough time to study, you can at least guess the details from your little background knowledge.
Do multiple choice last. You can always guess and have a 25% chance of getting something right even if you don't finish the question and just guess unlike if you miss out on the responses part.
Also -- only as a last resort -- if you're still not finished with multiple choice and there's no time to read, just pick one letter and choose that for ALL the remaining q's. If you pick randomly, there's a chance that you'll get all of them wrong. If you pick only one continually, you'll be able to get at least one of them right...probably unless you only have a few q's left.
Also, don't stress too much about it. Year 10 is more of a practice in formal exams for HSC if you're going to Year 12, or so I've been told.
SC isn't that bad -- it will only be bad once you start thinking it is, so relax and make the most out of your last years before being a senior (if you're planning on continuing) because this will probably be our last chance to laze around.
coughi'mtryingtosoundsmartcough
Just try to relax when your doing the exams. I found that effective. Go through the past papers rather study everything (it's toally useless). And SC doesn't even count towards anything, but it's a good practise of the HSC exams. (the exam conditions, the timing for each questions etc.)