Israel Hyman has been producing great video technique tips for years. I met him a couple of times at PodCampAZ and he is a great guy.
Take a moment to visit his site, Izzy Video. There is a huge amount of information there to help you improve the quality of your videos.
Learn how to turn a hard light into a soft light. Also, learn how to tell the difference between a hard light and a soft light. Check out the full article to read all the details about how to do that.
New Media Interchange 
Great how-to on diffusion lighting with demonstration of the effects of different ways to soften light. I love the reminders of what to pay attention to, as well as the quick summary at the end. Good use of specific products while explaining how they apply to the larger concept. This is a great demonstration of how to present a how-to video.