***IGNORE THE PREVIOUS POST, IT POSTED BEFORE I WAS DONE AND I DIDN'T REALIZE IT*
I rarely post on training threads, because it takes so long to actually describe what to do in real life. And then you have to say the same thing again in another post for someone who didn't read the first...but I'll do it right now.
I make sure all of my horses know how to stop, walk, trot, and stop again on the lead before I have them do it on the lunge. Doing it from lunge to the lead is going backwards. But anyways, this is how I teach them.
You need a dressage whip, or some sort of extention of your arm. You don't hit with the dressage whip, its just a reinforcement of pressure and reaches places your arm can't.
There is a pressure point right where the neck connects to the shoulder.
Horses will stop or backup if this pressure point is squeezed. This is how I teach my horses how to lead and stop without hauling on the halter. Squeeze this pressure point and once he backs up, release it. Praise him. Do this once or twice. Ask your horse to walk next to you. Lean back just before you stop, and as you stop, say "Whao" and reach over with your left hand and squeeze this pressure point. It might take a moment or two for the horse to understand how to make the pressure go away. After he stops, release the pressure and praise him. If you do it correctly, it should only take about 3 times before he stops at just a touch.
If he doesn't stop the second you touch him, squeeze that pressure point and make him back up a step or two. Release when he backs up.
5 times into your walk/halt transitions and your horse will stop without having to be touched.
Now that you have the stop taken care of, lets focus on the walk. When you ask him to walk, lean forward and step a foot out. You are the leader, and horses will follow the leader. When he sees you wanting to walk forward, he should respond and walk with you.
If you lean forward slightly, raise your foot like you're going to walk and he doesn't follow, reach behind you with your left hand (this is where the whip comes in) and tap him on his hind a little, while you click. The pressure from behind (whip) and the encouragement forward (leaning forward, leg ready to step forward), will cause him to step with you.
Walk around doing these walk/halt transitions. Never go more than a couple steps without halting. This will keep his attention.
Once you have mastered the walk/halt, then you can trot. By now, all you should really need to do is lean back and he will halt (since you leaned back before reaching for his pressure point). Since he is taking your lead at the walk (walking when you start to walk), he will take your lead to trot.
Start walking, and when you have a good working walk, start jogging. The transition to your jog should be slow and smooth. Raise your legs up a little to make your body bounce a little (make it appear like you are jogging) while you're at his walk pace, click to him, and his pace will quicken. If it doesn't, reach behind with your left hand and wiggle the whip a little while you're "trotting". Click to him. If this doesn't work, touch him with it and click. He will see you as the leader (he already follows you when you step forward) and will start to trot.
If he cranes to the side, stay with him. Stay right by his side, even if it means craning to the side with him. Slow him down and try again. Do not let him face you, stay by his side.
Expect him to burst into the trot the first time while he figures it out. This is where your halt comes in. If he bursts into the trot, tag his pressure point slightly and lean back. This will bring him back to the walk. Do a walk/halt transition to regain his ears and try again.
The second time will be smoother, but still choppy. And by the third, if you're doing it right, he should be with you. You can choose your speed as you trot. If you want him to slow down, jog slowly (tap his pressure point slightly if he doesn't get it). If you want him to speed up, jog faster.
This is how I teach all of my horses how to lead. After a day or two, I don't even need to touch the lead rope, or them. They are right with me in every stride. I lean back, they stop. I stretch my foot out, they walk. I pick my knees up, they jog. You can even teach them to back up if you back up, but that's a bit advanced for right now.
Only YOU can decide how much pressure he needs. With some horses, all I have to do is turn in on them and they stop. Some horses, I have to grab that pressure point and really shove before they get it.
Same with the whip. Some horses just need a wiggle, others need a tap. Still, others just need the sight of it. If you have a horse who just needs the sight of it, you shouldn't really need a whip since they are that sensitive, they should pick up on your movements right away.
Once you can control the horse's forward motion without touching them, then you can go onto controlling them on the lungeline.
This can be a bit daunting to just read, remember and then perform without being shown physically. But if you can get the walk/halt down, you can get the trot as well.
Hope this helped.
***ETD: Always stay next to your horse, NEVER infront. If you move infront, you'll end up just dragging the horse. You want to stay with your horse so he can see you and respond to your pressures correctly. You should never jog out infront of him and pull him into the trot. Stay with him and make him trot WITH you, not behind you.