Tips:
Make notes now for topics from Year 10 and continue that through Year 11 - that way when everyone panics because they have no revision resources you'll be ahead of the curve. Also try and organise your notes as much as possible! Try out different revision techniques and find the ones that work best for you (I mentioned notes before because flashcards is what worked best for me). Different subjects require different ways to revise though so for things like sciences and maths do A LOT of practice questions nearer to exams. Take breaks from revision but make sure you go over topics to ensure you can recall them. If you're doing a coursework subject DO NOT fall behind - deadlines will hit faster than you think - I did that and it wasn't fun. Though to be completely honest, GCSE's aren't unreasonably hard, recall is the most important skill for most subjects and one of the main things to emphasise is that everyone does differently in exams, so don't stress too much and just aim for your personal best - not anyone else's. Don't stress out if someone else in your class is doing heaps more revision than you and try not to get worried by the people around you. Oh and also if you are stressed about something take a break - trying to concentrate while panicking is like trying to walk on water. Year 11 shouldn't really get too stressful until exams hit anyway. Hope this helps.