I would say max three subjects a night- one hour per subject then spend more time on subjects which require more time. Take breaks every hour- 10min or so? So take a quick bathroom break, get something to eat, maybe check your phone (briefly) but obviously don't start watching a TV show or checking FB. I would say go to sleep at 11pm- 'studying' varies but generally to start off, make/read notes, then move on to answering questions and doing past papers/essays
