Depends on what learner you are.
Currently revising for my GCSEs (taking a 10 minute break after 1 hour) and I've done some biology so far this afternoon. I have targeted some computing revision tonight; and that's one key to revision success. I think a lot of people have the mindset that you should spend hours of revision then once you've done 4 hours of chemistry, then go on to geography. I have a slightly different approach. I target the topics I am uncertain about and once I am competent with them, that is when I'll move onto the next subject.
So how do I revise?
1. Specification (this is your best friend up until mid June)
2. Revision guides
3. Plain A4 white paper with pen, pencil and coloured pens/felt tips
4. Past paper questions
5. Flash cards
1. The specification allows you to see what you actually need to learn. This will help you focus your revision and stop your drifting away from what the exam board actually want you to learn. It's also quite useful for quick bullet points for your flash cards (come onto that later)
2. Revision guides! Very useful to refer to as it contains a lot relevant information.
3. I use these items to create a spider diagram. I will add some colour with some pens and felt tips but not a lot because it can be over-whelming for me. I will then create bullet points using my revision guides and specification, keeping them short and simple. After I have completed a topic, I will read over my notes again, ensuring I understand them
4. Test your knowledge! Fairly straight forward.
5. Once you have identified your weaknesses, make flashcards on your areas of weaknesses so you can then pull them out whenever and study them.
6. Remember to take regular breaks and to not stop revising areas you're competent on otherwise you will forget the information when the exam comes.
Hope I helped! I'm going to revise for computing now! Good luck with your revision and exams!