Make a game out of counting. Assess how much a child knows about numerical order by asking them "What number comes after...?" and then you name a number. You can make it into a challenge by asking them how high they can count and listening to the children count, making gentle corrections if necessary.
Make numbers a part of everyday life in a way that encourages counting, adding and subtracting. Ask the child to bring you five crayons and then only take two of the crayons, asking the child to count how many crayons he has left. Once she brings you the crayons, give her eight additional crayons and ask her to count the new total.
Play simple board games. Board games involve rolling dice, counting spaces ahead or backward and also keeping score. Always ask the child to keep track of the score and teach him how to make a tally, writing four ones next to each other and then crossing the fifth one diagonally across the others. This is a great way to teach a child to count by fives.
Start estimating the length of objects around the house or classroom. Ask the child how many inches they think a desk or table is and then measure it together with a ruler, recording the length in a total of feet and inches.
Ask the child to help you record her own growth. Measure the child every three or four months against a wall and ask the child to figure out how many feet and inches she is with a ruler. This activity can also be expanded if you give the child a plant and ask him to record the monthly growth of the plant in inches or centimeters.