If you're worried about GCSEs, wait until you start your A-Levels!
What I'd do after the summer term: focus in lessons, do homework/past papers etc, buy a folder and dividers (and label them accordingly), make sure your notes are clear/not dull and whatever else the TSR users are saying. If I had done that from the start of year 11 I would have achieved higher than the Bs I received..
When it comes up to your exams prepare a revision time-table and try to spend an equal amount of time on each subject. If you want, do past papers as well. Then you can see what you really struggle with.
Just focus though, these exams are actually really easy. They may not seem like it now but when you take A-Levels you'll really realise how babyish GCSEs were! During the April/May/June period where the exams are taking place and you're do heavy revision, and it's off-putting, remind yourself that you have a very long summer after. People underestimate how important these exams are for getting into sixth-forms. Some universities ask for good grades as well - i.e. As/Bs usually.
It's good that you're looking forward to your exams next year. Good luck.. my advice isn't perfect, but if I was given the opportunity to re-do my GCSEs that would be the steps I'd take to get all As.