How do you explain the concept of even and odd numbers to a first grader? any tips? ?

My teacher told me to take the number, 3 for example, and break it into ones. 

1 1 1 

then she said to imagine the ones are going to a dance and need a date. put the one together in groups of two

1-1   1

she then said if there is a one with no date the number is odd