Please do not recite a script written beforehand; just talk spontaneously as you would to a friend. People delivering memorized speeches (or worse: text off the screen) usually come off as robotic and stupid. Unless you're a good enough actor to fake spontaneity, you lose more in the stilted delivery than you gain from a more polished message.
The video should be one minute long and should be uploaded to YouTube. If you don't want others to find it, mark it as unlisted. Don't mark it as private, as we won't be able to see it, and don't want to bother with a password. Also, before you send it to us, please try playing it yourself, and check that you can hear what you're saying. A large portion of the videos we get are inaudible, so don't start your application off on the wrong foot. If you're going to apply, you should apply with a video we can hear and understand.