If I had to make a web marketing video today, I would think in terms of concrete images and language (see principle 3).
I would think about sound as a hook to keep you attentive.
I would think a about a surprise that you'll want to wait for.
I would think about giving you choices.
I would leave you wanting more...
Photo Credit: http://www.flickr.com/photos/onkel_wart/ / CC BY-NC-SA 2.0