The best way to study form maths is to go over past papers. You can find them on the BOS website. Papers found in your excel or school textbook are also helpful. Make sure you do them under exam conditions ie. 2.5 hours etc.
Once you have compleated the paper look up everything you wern't sure about or got wrong in your textbook and use examples to help you.
My textbook has 4 different Review Sets at the end of each chapter that cover basically every type of question in the chapter, so I study by doing them, and writing down which questions I got wrong. Then, I go back to the chapter and learn everything I can about the question I got wrong. Works so far.