I walk next to them and hold the reins in my hands at the withers, like I would if I were riding, but you could start ground driving which is longer reins and further away. Most of the kids I have ride are young so on lead line and they learn the voice commands. I also put reins on the halter rings, so the kids can steer & stop without hurting the horses mouth and that also teaches them. I need to get an "experienced" child to help move my mare to off lead, but she does pretty good by voice commands from so many years doing lead-line.