Writing a great script is the most important aspect of creating a great demo video. At Grumo we use a success formula for every video we create.

Your video should have everything in the "success" formula:
1. Simple
2. Unexpected
3. Concrete (is this solution/problem a real one?)
4. Credible (if a big name or personality vouches for your work)
5. Emotional (the most important aspect for making a video memorable)
6. Story
7. Smile

Your demo video is essentially an elevator/sale pitch but don't sound like a used car salesman. Write a script that sounds friendly and natural like you're talking to your best friend.