Well, my dd is only in year 7 at the moment, so I'm reading with interest. However, we received her school report yesterday and it is absolutely glowing, so I reckon we are doing ok so far.
My approach is to take a very active interest but to leave dd in control of her school work. We talk about what she is doing a lot, and also about what she has to do, how she is going to organise herself. However, the responsibility for actually getting it done is entirely dd's.
She has settled into a very good routine of doing it as soon as she has the opportunity - she chooses to go to the after school homework club three times a week, so this gives her 6 hours of concentrated time to get it done each week, leaving her very little left to do at home. It's a revelation to me, as I was always a last minute merchant! We do talk about some of her homework tasks, and we have a very good collection of reference books at home. Fortunately, dd's primary school set a lot of homework that involved independent research, so she has already developed quite good internet search skills.
With regard to organisation, we have a box in the kitchen for school stuff, but dd hasn't really used it at secondary school - she prefers to carry everything in her bag at all times so that she knows she won't forget anything! Makes her bag very heavy for the long walk to school, but her teachers do say that she is always well prepared for class! PE kit is the only extra thing that she has to remember, but I make this her responsibility and she never forgets - generally, she leaves it in her school locker during the week and just brings it home for a wash at the weekends.
She uses her planner effectively, writing homework in the day it's given as well as making a note of when it's due. She also stuck a copy of her timetable in there, in case she lost the other one. We also have a spare copy at home.
She is very bright and does exceptionally well academically, but we have never rewarded good results. We do praise effort, persistence and hard work, but again, no rewards - I have always tried to teach dd that success is her own reward, and that better heard work now will pay off in the future. We might sometimes celebrate her success with a nice family meal or something though.
I agree that it's really important to facilitate friendships and to encourage activities outside of school. To gradually let them have more independence and develop new life skills. And to be there for them without being too much in their faces!
The only other thing I would add is that we have always emphasised to dd that we don't mind how well she does at anything, as long as we know that she has given it her absolute best. My favourite one of her reports yesterday was from her PE teacher - PE is the one subject that really doesn't come naturally to dd, but her teacher commented that her attitude and commitment to the subject was outstanding. That made me very proud, and dd knows it. You can't be good at everything, but you can always try your absolute best!