For a review of the lean startup and customer development, see videos 4-1 to 4-3.
If you use a supported browser, you can view Youtube videos via the YouTube HTML5 Video Player, which may be more accessible for keyboard and assistive technology users. This can also be used to playback the video at a faster rate of speed.
Andrew Chen has a great post with an example of what I'm talking about with what can go wrong if you just blindly follow a technique but aren't truly thoughtful about what you're doing and why.
I can't emphasize enough that it's important to stay with testing the riskiest aspects of the business model.
Here is the post I mentioned by Manu Kumar at K9Ventures.