The only method I know of to improve one's math skills is to obtain a textbook containing the types of problems that will be encountered on the test along with their corresponding answers and then work the examples until you are confident that you understand what is involved in solving each problem type.
The Internet is another rich source of mathematic material from which to draw example problems along with their solutions.
Yes, the best way of improving Maths skills is by doing it - and lots of it. That way it becomes second nature.
Also try and reduce your reliance on calculators for addition, subtraction, multiplication and where possible division, try and do it in your head as much as you can.