If you want the boys and girls in your class to sit on the edges of their seats and be engaged in the Bible stories you tell, PRACTICE!
a. Read the story over and over. spend TIME with it!
The purpose is to absorb the story until it become second nature to you - so you can tell it from your HEART, not just by rote. Read the story as a whole. Read it from different Bible translations. Lose yourself in it. Think as you read - picture the story; set the scenes clearly in your mind.
b. Think about the characters
(1) What do they look like?
(2) What are their respective traits?
(3) Why do they say what they do?
c. Tell the story aloud to yourself over and over IN FRONT OF A MIRROR!
Do not concentrate on memorizing word for word -- although you should always know your first and last lines by heart for a comfortable start and finish. Become familiar with it so you can tell the story the story from your HEART, rather than read it.