Without seeming flippant, your number one priority should be to make sure it doesn't. The only reliable approach to this (at least with an immature product) is a 100% scripted demo that you have run through multiple times both in your office, and ideally where you are going to do the demo.
Ideally you also want to avoid using any sort of live/ad-hoc data if you can (you can trust that this is when an edge case is going to turn up!).
Script it, run through it multiple times and this will minimize the chances of anything unforseen going wrong. If you are not technical make sure you check off your demo with your technical guys so there's nothing they're uncomfortable with on there.
Make sure you're not demoing on either a dev or a live system if possible. You should have an environment just for demos which no-one else touches. Last thing you want is someone doing a release in the middle of it. Make sure the dev team know there's a demo planned in any case.
That said- inevitably things still go wrong, and most people accept this. Smile, and move on.
Ideally you also want to avoid using any sort of live/ad-hoc data if you can (you can trust that this is when an edge case is going to turn up!).
Script it, run through it multiple times and this will minimize the chances of anything unforseen going wrong. If you are not technical make sure you check off your demo with your technical guys so there's nothing they're uncomfortable with on there.
Make sure you're not demoing on either a dev or a live system if possible. You should have an environment just for demos which no-one else touches. Last thing you want is someone doing a release in the middle of it. Make sure the dev team know there's a demo planned in any case.
That said- inevitably things still go wrong, and most people accept this. Smile, and move on.