To get good marks in maths, most important thing is to practice more. learn all the formulas and try to work on it. many times you do one type of questions and by the time you will become king of that question. likewise you practice do every chapter thoroughly so that you clearly understood, and if any question of that type will come even from outside the book which you haven't even saw once, you can solve it easily because you have knowledge how to solve it. thus you can get good marks in maths.also try to get a book of learning easy formulas and for tricks of maths which can help a lot.