How do I select and properly fit a western headstall?

A western headstall is the leather framework that holds the bit in the horse's mouth and connects the reins to the rider's hands, and its correct fit is essential to both the horse's comfort and the effectiveness of the rider's communication. The bit position in the mouth is the most important outcome of correct headstall fitting, and adjusting the headstall specifically to achieve correct bit position is the standard against which all other adjustments are made. Most western headstalls are adjusted at the cheekpiece — the leather strap that runs from the crown piece down to the bit ring on each side. The bit should be positioned in the horse's mouth at the correct height for its type — a snaffle or loose ring bit typically at one to two wrinkles at the corner of the mouth, while a curb bit may be positioned with one wrinkle or even at the corner without a wrinkle depending on the trainer's preference and the horse's mouth anatomy. The cheekpieces on both sides should be equal in length so the bit hangs level in the mouth. The browband, if the headstall includes one, should lie flat across the forehead without pulling the crown piece forward onto the base of the ears. A browband that is too short pulls the headstall forward and creates pressure on the poll and behind the ears. The throatlatch, where present, should allow a hand's width of space between the strap and the horse's throat, permitting flexion and natural head movement without any sensation of restriction.