Color   
Implore your students to color their language with thought!

Learning lines is really answering the same question over and over again - "Why does my character choose these exact words?" Refining those answers is the main way an actor improves his performance. The more specific, refined and colorful the thoughts are behind the words, the more information will be conveyed through the voice. Speaking and acting is not about booming sound; it is about coloring and refining thought.