In lower grades, it is easiest to tell the kids a story that involves them such as one in which they meet up with friends. I used to tell a story, that the children dramatized, about them playing in the park. First kids A and B played together, then kids C and D showed up, later children E and F arrived, etc. As the story is told the students must tell how many students were present during each part of the story. Kids who are part of the dramatization should line up in pairs as they arrive at the park, so that they are easy to count by two's. The setting of the story can be modified however the teacher sees fit or by the students, as they come up with new ways to add to the story. By the end of the story the children should have at least counted all the members of their class in pairs. This story can be modified to use to count by any other number depending on the number of students in the group that arrives at the park together: 3's, 4's, 7's etcetera.