Fixing My Deadlift Form

I was watching a video that explained the form for doing deadlifts, and I realized that I do something wrong. When I’m about to lift the weight I always tend to first straighten my legs then pull up with my back. I’m not sure if that’s how it’s supposed to be, but if it isn’t can someone explain how to fix this? I think it’s putting a lot of stress on my back which is why I can’t lift much.

http://www.T-Nation.com/readArticle.do?id=1588392

Read part I and II.