Use flashcards. Write a question on one side of a card and the answer on the reverse. Shuffle the cards and pick them up one by one. Work out the answer and look to see if you got it right. If you got it correct, place to the side. If you got it wrong, place it back in the pile. Repeat until you have got all of the answers correct. You can do this with a friend to make it more fun.
Make a poster to put on your wall at home. If you struggle with the relationship between circumference, diameter, radius and area of a circle, make a poster that has a circle with each term labeled. Use a different color for each term.
Ask your math teacher to help you in areas where you struggle. Write down parts that you find difficult, and approach your teacher at the end of a lesson. Your teacher will be pleased to explain it to you.
Use math as much as possible. When you are in a store, work out how much your items will cost as you shop. When looking at your watch, work out how many minutes you have been doing a certain activity and how many seconds this is. Constantly doing math will improve your brain capacity.