I try and teach every horse I work with to ground tie, it makes them stand so much quieter when they're actually tied up. I start off with a rope halter (I prefer the clinton anderson type that are thinner with the 2 knots on the noseband- you have a lot more control that way) and I make sure the horse knows how to lunge well (basically move to pressure), especially how to back up if I wave the lead back and forth. When they're standing in the barn aisle (or wherever I tack them up) I stand in front, drop the lead rope, and say Whoa. From then on it's just a matter of correcting them whenever they start to move. -you really can't leave them alone at the beginning since they don't really know what's going on. If they start to walk off I back them up (sometimes harshly), get them to where they were to start with, drop the lead rope, and say Whoa. You can't let them put their nose on the ground to smell stuff because 9 times out of 10 they'll start following their nose somewhere! I also don't let them turn to the side and start sniffing things, they need to stand still quietly. After a while (depending on the horse) they start to figure out that the lead rope on the ground means stand there. Once I left my horse out in the aisle and met the vet for something and completely forgot about him standing there! 20 minutes later, went and got another horse and then found him standing like an angel (mostly sleeping actually)! Haha, OOPS! Not something I recommend!
but it's great that I can leave him there and he doesn't get into trouble. It's also great for when I'm setting up jumps in the arena. I leave him in the middle of the arena, set everything up, and go get on. And I come from the background where you never ever leave the reins or lead rope hanging on the ground? I still agree with the reins, but if the horse steps on the lead rope it's not a big deal. They start to pull back, the smart ones who know how to give to pressure will put their head back down and move off of it. The others kind of snap their head up and jump off and then realize it's not a big deal.
This is the way I've done it, I'd love to hear the way other people ground tie.