For example, give them a monologue like "The Not So Perfect Child" by D. M. Larson. http://www.freedrama.net/notperfect.html
This monologue has a child dealing with being angry at her mother and older sister. The teacher / leader could have students try to show the right emotions for the monologue (anger, sadness, etc.) and then try to show the right body language for the character.
"No Witnesses" is another good monologue with someone who is hiding a secret. http://freedrama.net/nowitness.html
And some good monologues that deal with relationships with boys and girls:
"Before You Punch Me" http://www.freedrama.net/punchme.html
"Breaking Heart" http://freedrama.net/breakheart.html
And some good monologues that deal with feelings of appearances:
"Perfectly Ugly" http://freedrama.net/perfectugly.html
"Piggy Princess" http://www.freedrama.net/piggyp.html
Finally, some other good monologues to deal with other emotions about family:
"Beauty and Perfection" http://freedrama.net/monoshelly.html
"First Words" http://www.freedrama.net/firstwords.html
"Mess Things Up" http://www.freedrama.net/messup.html
"Sob Story" http://www.freedrama.net/sobstory.html