HowToCreateDemoVideo

To make a good demo video please follow these steps:

Think about the problem your tool address, how does it solve the problem, why it is convenient, cool, etc.
Put this as a demo script in a text file, like this WHDemoScript. Include info about the project, where to learn more, etc. in the script (or slides, if you use them during the video)
Print the demo script and rehearse it several times, making demo on your screen (so that you are able to read the script fluently and you are sure there are no bugs in it)
Demo video should be 1-2, 2.9 minutes, no more!
Install some program for capturing video from your laptop, for instance Debut Video Capture Software. The great thing about Debut Video Capture is that you can set up start/finish of the recording as hotkeys, so the program does not appear in your video. QuickTime Player is excellent to record videos using Mac. Both Debut Video Capture and QuickTime are hidden from the screen when you are recording.
Chose a quite place, otherwise you can listen disturbing sounds in the background
Use a professional microphone, you can find one in Room 6 in the right part of the drawer on the left from the entrance (Michela has a key). Instructions on setting up the microphone.
Upload the video on youtube and tag it with "LiquidPub" and other related tags to make it easier to find. Example.

note, that the video used in the example is not actually great, in the future it should be replaced by one of LP videos:)

Examples of good demo videos

Any Google demo video is normally good, check this google doc video, for instance.