"Tricks of the Trade" are useful in any profession, and are as well in the art of public speaking.
TRICK: Look in different directions to indicate different characters. The audience will associate a stage right or stage left look with the different character.
TRICK: Use above trick along with changing your voice tone to indicate different characters.
TRICK: Use different postures for different persons, body language can speak loud and clear.
TRICK: Do what the written story says. If it says Joe cleared his throat, you clear your throat at that point in the story.
Without saying a word, you can communicate loudly when you use body language in the art of public speaking.