People don't normally start taking GCSEs too seriously until year 11, so I wouldn't worry too much for the time being, although it is good that you are aware that effort will need to go into it, eventually.
Each subject fits a different revision method, but I generally find that using flashcards/information cards for subjects such as geography, history, English etc are good, and past paper questions for maths and science in particular are your best bet.
Don't start off at too fast a pace or you'll burn yourself out before you get to year 11, but good luck!