- Practise exam questions
Timed practice papers and working through textbook questions, particularly the topics that you struggle the most with, until it becomes second nature is the best way forward.
You can find past papers online if you search for them on your exam board's website and there are plenty of study books you can buy to help you revise.
Put in a little work every day, even if it's just 15-20 minutes of maths work on top of your homework.
Good luck with your mocks!