Keep on top of practicing what you've been taught each week by finishing all the available questions - Maths is the kind of thing you learn by doing rather than just revising how to do. I was not very diligent about finishing the exercises set in class each week and my grades in topic tests were hovering around a B/A - when I actually started finishing things I started getting secure As and sometimes A*s. Keeping on top of it also means when it comes to revising you just have to refresh your memory of each topic as the skills should already be there, rather than having to basically learn it all again because you didn't learn it properly the first time.