We will assume you already have this 9-month-old halter broke to some degree. To show at halter, he will need to lead at a walk and trot and set up. Remember, when showing at halter, the conformation of the horse is judged, not your showmanship ability. Therefore, you are allowed to touch and set the legs with your hands.
We suggest you lead the colt alot and keep him quiet. Teaching the colt to back away from you will help when you work with him to set up. If the colt pushes on you or tries to run over you, then make him back away. At this stage, it is also very important for the colt to learn that "WHOA" means to stop. In working with the colt to set up, lead him forward and let him set the right hind foot. Then rock the left hind foot forward and backward to get it close to the right foot. Then you can use your hand to set it in the location you desire. You can also pull the hip or tailhead to the left to encourage the colt to stand down on the foot. After setting the hind feet, do the same with the front, and go over to the right side to set the right front, and move to the left side to set the left front. Constantly use the word "WHOA" during this entire process so the colt understands he is to be still.
The colt will most likely move some at first. Be patient and keep working at it. Other basic handling/gentling methods such as sacking will also help the colt become more accepting to whatever you are asking of him. The key is a lot of time and patience!