I wouldn't start like intense revision right away but a great thing to do is to right up revision notes for subjects like English Literature to summarise all the things you need to know: quotes, themes, characters etc. If you do a language, Quizlet is a free app which is great for learning vocabulary (definitely worth revising vocab off the list provided by the exam board as so many unique, irregular words came up in my French exam that I wouldnt have known without doing that). Maths - PAST PAPERS and Mathswatch if your school provides it. Sciences - mygcsescience is a great website for revision videos (core is free but you have to pay for additional and triple videos) - he has made videos specific to the new science 9-1 gcses that you will have. Hope this helps and good luck for year 11 !!!!!