Youtube is such a good resource for improving your weightlifting. I wanted to put up this brilliant video, which features slow motion footage of various 69kg lifters snatching. Of particular note is the contact of the bar at the hips. This explosive effort to contact of the bar once it has passed the knees it what drives it upwards. There is a distinct difference between the pull off the floor and this explosive second pull. Immediately following this explosive hip and knee extension, there is dramatic hip and knee flexion and a driving down of the body under the bar by the arms. The arms keep the bar close and moving in a straight line, finally punching out to lock it out overhead. All effort is directed into moving the bar up then moving the body under the bar.