I know this wont help - but with the majority of subjects, study is about finding what works for you. Obviously, things like notes/past papers are pretty much universal methods, but the exact specifics of how to do past papers/write notes varies from person to person. Thats why studying in the earlier years (10 and 11) is important, because you use it to master your study technique.
I know I've said this a million times on this site (sorry to be repetitive), but in terms of getting motivated, try setting small achievable tasks instead of setting huge slabs of work. Achieving your study goals will help get your confidence up, which will increase your willingness to study.