Be on time. Be prepared. Be organized. I have fallen short with each of these elements at one time or another. After 7 years of teaching several related courses to prepare students for our specific industry, I have made many mistakes. But if it is one of the essential elements above, it is more serious than any other mistake I have made. Sometimes my demo is not perfect. So what? I tell them that it is not, and tell them why. And during their production, I watch over them to make sure they are working toward not making the same mistake I did. It is always nice to have a perfect demo, but it just doesn't happen every single time. So I strive to work on the main things that will help me avoid mistakes: timeliness, preparedness, and organization.