One great way to teach it is by using math worksheets. One could make worksheets that are fun for children to complete. Adding graphics such as fruit and candy and having the children add them up will open their minds to it and have them learning in a fun way. Also, the sense of accomplishment the child has after completing the math worksheet correctly will encourage him to continue learning the subject.
This affords me the opportunity to publicize World Maths Day which took place on the first Wednesday in March. There students of all ages from all over the world went online (it's free) to play mental math against each other. Last year 287ꯠ students from 98 countries participated to answer over 38 million questions. This year they hoped to break 50 million questions and did so magnificently answering over 150 million questions and I am sure they had great fun doing it.