Choose child actors whose personalities match the characters closely. Guide them through an imaginary story. While you narrate the story, have the children act out the characters in your story to gauge how they take direction.
Rehearse adult roles prior to bringing in child actors, as the children will perform better if the adult actors around them are more secure in their roles.
Bring children into the rehearsal process to accustom them to the action of the play and to develop relationships with the adult actors. For example, in the musical "The King and I," the young actors who play the king's many children can develop their roles by following the lead of older actors.
Be flexible. Long rehearsals and technical schedules can wear out a young child, so make sure to vary rehearsal techniques to keep children engaged, and only bring them in when they are needed.
Have a "child wrangler" backstage, someone who looks after the child actors when they are not onstage, keeping them prepared and entertained. This should not be another actor in the show.
Prepare children for performing through creative drama games. One good warmup game from ChildDrama.com is called Nursery Rhyme Charades. Start by having children name nursery rhymes they know. Then guide one student through a pantomime of action from a nursery rhyme, while other students try and guess which nursery rhyme they are pantomiming. Give positive feedback on each student's pantomime.
Guide students through performing a story. You can use well-known fairy tales or find cultural myths appropriate for children to provide multicultural education in addition to dramatic education. Cast students in various characters and narrate the story while helping them act out each scene. Build on the pantomime techniques from the previous step.
Gauge the concentration and ability level of your students. If you feel they are ready, guide them through creating an improvised story. Set up the story by giving them a setting and problem. For example, a group of students and their teacher are on a field trip and the bus breaks down. The students can decide who their characters are, which allows them to use their creativity and add color to the story. Let them work together to solve the problem.
Have the students perform a previously published story as in step two, or perform their guided improvisation for friends and family. You can enhance the performance by bringing in costumes and props to help students develop their characters.