Hum and Sing
Ask the child to stand in front of the group and instruct him to open his hands when he wants the audience to sing and to close his hands when he wants the audience to hum. Play through the song and encourage all the children to keep their eyes on the volunteer. After one round of the song, choose another child song leader who sang the loudest or the most reverently. After a few run-throughs of the song you will know where the primary group is weak on the lyrics and will be able help them memorize the song.
Memorize with Your Hands
Ask the children to create appropriate yet simple hand actions for each sentence or idea a newly introduced songs to help the older children get involved. Choose an action that the children and you can easily remember. Incorporate the actions into song as you sing. Have the children use the hand actions every time you sing the song until the children know the lyrics.
Test Lyric Knowledge
Write the lyrics of a the song on a poster. Leave several words blank on the poster so each child in the group can fill in at least one blank. Duplicate the poster, choosing different lyrics to leave blank for the other groups. Divide up the groups in Primary and give them the poster and a penny jar. Instruct each group to allow each individual one chance to write a word in the blanks. When the individual correctly writes in a word, they can put a penny in the jar. Tell the children that everyone present will be continually singing the song on the poster until a team finishes filling out their poster correctly and has the most pennies.