Before a horse can change his lead, he must balance himself. Don’t try to chase the lead; balance your horse onto his hind end and make sure he is relaxed and going at a small to medium canter before you ask for the lead change. Also make sure that when you ask for a lead change, you keep your aids clear and simple – don’t overdo it. Sometimes if the rider uses excessive aids it can confuse and upset the horse, so try giving your horse a chance to change his lead on his own. Do a large figure eight and see if the horse can do it by himself without you asking. Simply sit quietly and see if your horse will do it automatically (many well-trained ones will). Ask your trainer or an experienced friend for more help if needed. Good luck!