I did this with my horse and its very similar to join up but easier as you are encouragihing your horse to follow you.
Lunge like normal with a long rope and start walking towards your horses bum at an angle but not close enough to be kicked than ignore him and walk away with energy and relaxation (in the direction you were facing the horse), keeping your posture good. If your horse is actually listening to you they should follow you as you have just lunged them and they should be following your direction, if they are being respect full and following your direction when you walk away they still should be following your commands and so the horse will follow you as they are asking what direction next.
So you can also change it up by adding serpentines in, encouraging the horse to do a smaller circle around you on a lose lead and ect.
You also can keep repeating the exersize but make sure you keep it interesting for both of you.