A few tips I have would be to always keep the line taught, slack in the line can cause a tripping hazard to you, as well as the horse does not have any sort of contact on his face, which is important because you need to have control.
I always try and stand at the shoulder line (much like when just leading) and not let the horse go to forward, or slug behind. I also move my feet quite a bit, but not in a huge circle, they stay at one spot and I just turn around.
I also make a V (like the drive line previously mentioned) shape with the whip and lunge line, and always trail the whip behind but never use it. It acts a reassurance so the horse knows that he is working. By creating a V with the line, it almost makes a box around the horse, where you have control. If he's too slow you can bring the whip a little closer and if he's to forward then you can move the whip back to let him relax.
I also keep my feet in the same spot more or less, just turning around with the horse.
Hopefully some of these tips help you as they have helped me :)