Start your new horse with one rein and a rope halter. It makes sure your cues are clear and doesn't confuse them. The first thing to do is make sure the horse is desensitized to the rope. You should be able to toss the rope up and around its head and not have it respond adversely. When you get on top of your horse, whichever side you tug on the rope should have your horse flex in response. Its head should bend to the side. It may be daunting at first to train your horse on one rein, but doing so will build confidence in both you and your horse. If your horse will listen to you on one rein, it will listen to you on two.