I'm putting together an e-book on the Five Fist Postures of Hsing-I Chuan. It will be given free to everyone who purchases a copy of the new Hsing-I DVD on the fist postures through the website (even people who have purchased it in the past will be sent a copy of the e-book when it's done).
One of the techniques to practice when doing any of the three internal arts--Hsing-I, Tai Chi, or Bagua--is to keep the hips under you as you move. I meet people all the time who violate this principle.
If you watch carefully, a lot of martial artists leave their butts lagging behind their torso when they step forward. Some of them really drag it.
Sometimes, to demonstrate this to students (because as we all know "it has to be shown" and can't really be taught through videos and books), I'll have them push on my lead hand as I go through the Pi Chuan fist posture.
As you practice any of the movements in your internal arts, I hope you have a mirror handy (or a video camera). Watch to see where your hips are as you go through your movements. If they don't stay beneath you, experiment with the movements until they do.
The e-book that goes with the Hsing-I DVD will contain well over 100 photos from the video. It's designed to be used as a reference tool.