Lots and lots of ground work!
When you are lunging your horse (either on a line or free lunging):
Work on your voice commands (walk, trot, lope, WHOA!). Once he is responding well to your commands (especially Whoa, I can't stress enough how important that word actually is), you can start using a cue. Every time you ask him to whoa, tap your leg (like you would to call a dog) and turn sideways to him. If he doesn't come (or attempt to come), work him some more. You may see chewing, ears flicking, lowering the head, licking - these are great signs that he is listening to you and starting to become submissive (remember you are the lead mare
. Keep stopping and asking him to come to you. It takes TONS of patience, but work your way up to it. Even if he only takes 2 steps towards you at first, its a great start. However, do not stop lunging until he at least makes an effort to come to you - if you stop too early, he's going to learn he doesn't have to come to you when you ask. After several lunging sessions, you'll see a great improvement out in the field. But always do the come command whenever you lunge - horses are creatures of habit and have to be reminded constantly!
Anyway, hope this helps. I know it worked wonders on my mare!