Revew-A class presentation

I watched A class presentation. I found two important point when speaking English. First, big voice is the most important point I think;because, if speaker' voice is small, listener can't understand and get bored. Second, facial expression is also important. Some students glanced note and no smile.I think if speaker is smiling , listener can relax. Student in A class are used to speaking in public. When I speak English in public, I sometimes get nervous. I want to be like them.