Write down a set of math problems. Since you're practicing basic math skills, these only need to be basic multiplication, division, addition and subtraction problems. You can also make them up on your own, since they are so basic.
Practice as many math problems as you can for a set amount of time each night. A half-hour is perfectly acceptable, as long as it is consistent.
Increase the difficulty of the problems. Start with single-digit problems to boost your confidence, then make them harder as time goes by.
Calculate math problems in your head. Whenever you see numbers, make a math problem out of them. So, if you look at the clock and it is 12:30, try to multiply 12 by 30 in your head. Do this at every possible opportunity, and your math skills will improve over time.