Mathematics is all about practice. You will need to keep solving problems to identify your weakness and strengths and work on them accordingly to thoroughly understand the concepts. Solve subject specific questions and then progress to past-paper questions.
Furthermore, time management is also a key component when solving a math paper. The time invested on each question is crucial because you might not have the time to answer the other problems. To do this, pay close attention to the command terms in the question and use your formula booklet and GDC appropriately and efficiently.
Lastly, make sure to start practicing and studying well in advance for your exam for at least 30 minutes to 1 hour a day. This should start a week prior to your test because cramming the syllabus the night before will not help you ace the subject.