Learn how to answer questions, in the sense that you may know the answer but you may not convey it properly to the examiner.
Eliminate silly mistakes, especially in maths.
If you learn to think on your feet, maybe through AMC or something else, A level maths and physics will mostly be trivial. Then you can focus on details.
Work with your friends, compete mostly with yourself and help each other improve.
Do challenging problems, make sure that you find A levels easy and the main issue is precision, details etc and not understanding big things by the time you start revising.
Do AMC or other competitions properly/or other challenging problems, practice them. The reasoning shouldn't be difficult if you practice enough. Then A level maths, should be straightforward and focus on eliminating silly mistakes.
Get comfortable with calculations by doing harder questions. Maybe use Olympiads etc Be precise when answering questions, there's no need to write a paragraph, just ensure that you mention all the points.
Do mind maps, put them around your house with the aim of looking at them casually once in a while to remember everything. If that doesn't work for you, just aim for some way of passively remembering things.
Ask your teachers how to improve your spelling, sentence structure and ask for your better friends to read their answers.
Here is an inspiring Story that Rohan is sharing with you...
I did not really work for becoming a Laureate (I did work, just not really for that goal). Competition is high and silly mistakes, imprecision significantly pulls you down. The advice I gave was mostly what I did during high school, and it worked for me, though the intent was never related to A levels/Laureate. During my cohort, a lot of my friends were also Laureates and I think the main reason why we did so well, was because we worked together and with teachers. The point of working towards being a laureate, to me at least, would be to be good enough to get into a top programme, get a scholarship etc. Keep in mind this is only one way to get a scholarship, but working towards it makes you a better candidate to other scholarships at the same time. My advice is towards, students who are very good and are not challenged at school: Make it challenging for yourself, go find harder questions yourself, so you can enjoy learning things. When it's time to memorise, it will be a pain but it's only for a few weeks/months. It might seem pointless but put your ego away and realise that being a laureate is a chance to bridge to more challenging environments. To make it less boring, simply work with friends. Maybe one last thing that applies to everyone that may be useful is that you should know the specifics of your weaknesses and strengths and work with and around them. The advice I gave, is mostly for a specific type of student, it might not be suitable for everyone.