How do I teach a horse to lead correctly on a lead rope?

A horse that leads correctly walks beside the handler with slack in the lead rope, stops when the handler stops, and does not lag, rush, or drift into the handler's space. Teaching it requires that you be clear about what correct looks like and consistent about correcting everything that is not correct, every time. Position the horse so its head is even with your shoulder — not ahead and not behind. If the horse gets ahead, stop immediately and back it two or three steps to behind your shoulder, then walk forward again. If it stays correct for ten steps, that is ten repetitions of the right answer. If it lags, a cluck paired with a swing of the lead rope end toward the hindquarters drives it forward without you turning to face it. Turning toward the horse to encourage it forward inadvertently teaches it to stop and face you, which is the wrong response. Keep your eyes forward and drive from behind. Changes of direction teach the horse to pay attention to where you are going: make frequent, deliberate turns without warning and let the horse learn to watch your body for cues rather than walking on autopilot. A horse that leads well does so because leading has been practiced and corrected consistently — it does not develop on its own through repetition of sloppy habits.