a year ago i was in a play with professional actors an other kids. we were putting on the musical OLIVER TWIST ,  and i picked up a few things after watching the recorded video that will help you if you are new to theatre or performing on stage:

• never have your back against the audience , EVER.
• dont look at the floor unless its part of your role.
• always be clear of what you are doing so people don't get confused or bored.
• always express yourself in your character.

and of course make sure your having fun.