cshar
Definitely! Make sure that you're passionate about at least a few of them as they do look at your CV while interviewing you. I remember I got asked to point out which of my achievements I was proudest of. I was able to relate it to my culture but relating it to a hobby or passion is probably event better. Unfortunately, for the interview itself you can either get really lucky or unlucky with the interviewer so you want a solid CV to boost your chances. Some examples of desirable achievements might be: Academic Excellence Awards (or the equivalent of student of the term/year), ICAS distinction, Australian Maths Competition distinction, NAPLAN certificate of achievement etc.
As for participation, do some volunteering if possible (could be something as simple as Clean Up Australia Day) and join some school clubs if your schedule allows. Playing a sport or instrument will also give you some leverage, especially if you've won awards for it.
I'm glad you're finding the tips useful! I'd be happy to answer any more questions if you have them!