hey,
I currently study A-level R.S and its actually my favourite subject. What helped me was getting my head round the structure of the course for example the different units and the that helps you revise. revise a unit at a time; I quite like mind maps, I read somewhere that you're brain responds better to curvy lines! Do all you're preparation before the exam and use that 15 mins in between to de-stress. either sitting on your own or maybe talking to your friends whichever works for you.
when revising have a plan! but also make sure you have some down time like trying a new activity just for like twice a week; e.g Yoga
hope that helped!