You practice your Presentation (material), you practice your Presentment (style), but do you practice your Props?
Props are those things that support your presentation. They could be pictures, graphics, PowerPoint slide decks, or demos.
Left unattended or unpracticed, they could spell ruin to your presentation.
Bill Gates and Steve Jobs had bet-the-business product debuts publically de-railed by mal-functioning demonstrations. In this age of instant video and social media, a faux pas in your demo could go viral with you becoming the butt of jokes on the morning news the next day.
Practice your material with your props. The night before, make sure your Props are in order, ensure demos and examples work. If you are using computer networks, make sure to have and use your own, and secure them to ensure you are the only user.
Forget your Props and they will bite you. HARD!!