I always tend to just study for biology and chemistry cos English is boring as hell, same as modern and generals just easy. Hmm should prob stop doing that.
I spent most of my time on chemistry -> ext 1 maths / ext 2 maths -> biology -> english.
The only study i did for chemistry was attend weekly 2hr tutoring sessions at a college and then do the homework which would usually take me an hour or so.
For ext 1 maths I would learn via mathsonline and then do a STACK of past papers
For ext 2 maths I'd do the homework set by my tutor and STACKS of past papers.
For biology I'd just read over my notes before exams and then look at a few sample answers.
For english, throughout the year I would have prepared top response answers/essays, and before exam time I would spend 2-3days memorising them.
So basically, no need for constant/consistent study.. but in saying that.. that was what worked for me and I probably have a little above-average memory.