Basically, if you were good at independent study in high school, you should be more than well equipped at uni. Lecture notes and textbooks should be sufficient information; tutes are more for knowledge consolidation, although if you're on top of the material you probably won't learn all that much from them (ironically they're the only component that is compulsory, usually). Just quietly, cramming is also a completely viable tactic at uni - as long as you're smart about it, you probably can get reasonably grades around here with a lot of last minute work.
In terms of getting good grades, it depends on the subject. In Commerce/Science, a lot of it is based on just answering questions correctly (because the assignments are just problem sets, etc.). In Arts, you need to be able to a. think well and b. write well, and to a lesser extent know what your markers are probably looking for. I imagine the same goes for written assignments in Commerce/Science/whatever.
To get lots of high distinctions, just keep up with the material and use tutes for the limited utility that they serve (at this end of the spectrum I mean; if you're a student looking for constant HDs tutes probably aren't going to be all that useful). Personally, I mostly used tutes to confirm that my ideas were all right and not totally off-the-rails. Also, don't be afraid of asking for remarking - I had a friend who got an exam changed from mid-60s to about 90% because the tutor was pretty much incompetent.
I personally believe getting a 70% average isn't that hard at all if you're a fairly good student and work hard. Most of my conscientious friends (ie. people who did what I just mentioned) ended up getting mid-80s averages this year, whilst maintaining reasonably active social/co-curricular lives.