Full extension on cleans
Yesterday I was in the gym with a pretty experienced lifter and strength coach. He wasn't there to coach me; he just happened to be in the gym and has given me pointers before,. He told me one problem with my clean is that I'm not getting full extension and am not using my hips enough; basically, that rather than using my legs/hips and traps to get the bar up, I'm abbreviating the movement a little and pulling the bar with my arms. He said that I wasn't doing it a lot, but enough to make a difference, and that it's a common technique problem for newer lifters. What are some good exercises for fixing this? Recently, I felt like I wasn't getting under the bar quickly enough, that I lacked the confidence and speed to get under, so I started doing high hang cleans. I think that's what they're called - I held the bar standing straight, with everything extended except for my traps, and just shrugged the weight up and ducked under. Those really helped a lot, and I now feel comfortable getting low on cleans. Now, though, I'm wondering what would be a good fix for not extending enough and using the hips. Any suggestions?
(I know a video would help a lot, but I'm a complete luddite and don't have a digital recorder).