Ask HN: How do I create a video demo?

I've been working very hard with bringing out our software product and now finally did it today. I am running out of time and I now need to create a nice demo video for this and start presenting it. Unfortunately I've never done a product demo video before and now need to do it fast and good.

Do you have any suggestions to how I can shoot my product video?

- Any consultancy who could help us shoot or edit my shoots?

- Any software that I can use?

I am on an emergency timeframe so any helpful recommendation to do this in a short timeframe would be greatly appreciated.