I stepped foot into the Hargrave-Andrew library (or the other way around, whatever) on the hunt for quiet study spaces. Omg, this library was so loud 
Wtf happened to library = quietest places on earth ?!
As I said in my Jaffy guide, the libraries are actually some of the more noisy places on campus. The very far reaches of the backs of HAL are alright, the rest is pretty noisy.
Will there be tutes in the first week?
More unusual for first year units. Less unusual for later year units, i know every single one of my units has a lab/tutorial this week. It'll be said in the first lecture, on moodle/in an email or on your timetable. Hopefully, at least one of these will inform you.
Do people generally go to campus on days when they don't have classes/tutes?
I have Monday and Wednesdays off and am tempted to stay at home and chill but I think there may be a better way to spend my time?
What is there to do on campus when there's nothing to do?
Depends. I'd wager most students don't, especially as you get older/more into your degree.
Days off are glorious, you dont have to put on pants. In particular, if you live 2 hours (one way!) like me, you are not going in just for shits and giggles. I suggest you stay home. If you find yourself falling behind in lectures or work, maybe make one a designated study day to go in and hit the library.
some units have lecture attendance as a hurdle. I think that's the case for most of arts units. We don't have such thing in engineering and science. In fact I didn't go to half my lectures last semester (not recommended)
ps: maybe that's tute attendance..whoops 
Nah, it's tute attendance. You cant miss more than 2-3 without failing in a lot of units. I've never been in an arts lecture that needs attendance. One wasn't recorded though, so, i did have to attend as a psueo-requirement (otherwise id just never hear the lecture).