It's best just to find the right balance that works for you. For most people shutting themselves up for the entire year and just studying isn't going to work, and is only going to make you burn yourself out and ultimately not perform to your best.
What I used to do once I got home from school each day was make a 'to-do list' with boxes that I couldn't check off until I'd done whatever the study I needed to do. This way I knew what I wanted to accomplish that night, and when they're all ticked off, I knew I'd put enough effort in and learnt what I needed to learn. I try'd to make the activities on the to be specific, so say 'I'm going to do exercises 3D, 3E, 3F'. Most of the time the work got done and I understood what I needed to learn. With that being said, you still need to find a time to take a break somewhere. Something I've been doing lately (didn't do in year 12, I should have though), is going for say 45-60 minute walks/jogs. Its a bit of fresh air, you don't get yourself couped up at home all the time, and can just go and refresh yourself. Then when I get back home I can get back into studying with a fresh mind again (plus my fitness is going up a little bit over time).
On the comparing marks and such, if you want to compare, then do it, but if someone else doesn't want to tell you what they got, then thats their decision, and people should (and will unless they're douches) stop asking. For some subjects it wasn't good for me to compare, for others it was but only with close friends which I knew were at similar levels. Although most of the time for spesh and methods everyone found out what I got since I was getting the highest for most of the time..... teachers... anyway. If it really bugs you comparing, then don't and don't let other people make you feel bad for not comparing. Its
your decision and
your mark, not theirs.
A few of us helped each other out over the whole year (I swear I spent more time in methods classes helping others than actually doing my own work, which I did mostly at home, but then that was kinda practise for tutoring I guess). It depends on the culture of the school you'er at I guess. If people keep to themselves and don't help others, then its hard to form study groups. BUT it only takes a few people to start off doing that, and when your marks go up from helping the others, everyone else may eventually realise and change. The culture needs to shift, its just a matter of starting that shift. There probably is someone there willing to do the same thing you want to do with helping each other, you just have to find them

(gotta try and rap this mess of ideas up

) In the end its just keeping a balance between studying and life I guess, which for this year may be shifted towards studying a bit more, but you have to maintain other things aswell.
EDIT: Oh and as said previously, keep a good sleeping pattern! Don't sacrifice too much sleep! My friends wondered how I could pick up ideas and such so much more quickly than they could, but it was more due to them having very low hours of sleep, and well they couldn't learn efficiently because of this.