I went to a Clinton Anderson tour this summer and he had a very good explanation on how to lunge.. Let's see if I can remember at least half of it...
The way he teaches it (or the way I
understand it, anyway):
1) point high (with the hand that has the lead rope in it --in the direction you want your horse to go.) If he doesn't go, don't panic. Horses that are first learning this just think you're crazy pointing toward the air. Don't skip this step, though, because if you want your horse to be able to lunge by just pointing, you're going to have to do this over and over!
2) click your tongue. again, horses starting out probably won't go with just this, either.
3) use a lunging whip or the end of your rope and spank the ground behing your horse. he should be moving by now. If not, spank the ground harder and harder until he does--eventually actually spanking your horse if you really have to.
Once your horse is moving, stay behind
the 'drive line' (which is his ribcage/shoulder area) to encourage him to stay moving. If he wants to stop, encourage him a little with clicks and if necessary the whip/leadrope. To Stop...
1) switch hands with the leadrope and the whip ...up until now you should have had the leadrope in the hand toward the way you were going. (I.e. if you were lunging clockwise, your right hand)
2) step in front of the 'drive line' and (for lack of a better word) 'pull' the horse's head so it's facing you and verbally say "yeild" or "whoa" or whatever you want to say.. Just make it consistent.
3) if horse doesn't turn it's forequarters toward you and stop, use the whip and encourage him to stop the motion--almost like putting a barrier there so he doesn't want to go farther... So hard to explain! To change direction...
1) same as step 1 in stopping...
2) Step in front of the drive line, pull horse's head around, encourage with whip, point with that hand (just like you did before), click, then spank if necessary.
He should change direction and eventually you will want to have him doing a rollback to change direction, and you won't have to pull his head around.. You'll just have to point the other direction, you know?
This is ridiculously hard to explain--for me anyway!
I'm sure I have a video somewhere of me lunging my horse.. I'll find it ...Otherwise just search youtube for "lunging for respect" and you'll probably find exactly what I just tried to explain. It's way easier to watch rather than try to decipher my vague description of how to lunge! It's kind of just trial and error- see what works best for you and your horse..
Good luck and hope I helped a little bit!!