I started the showmanship/halter training of my filly at week one after she was born. It was just part of the regular handling. When I led her I would always stand on the both sides with equal amount of time. I would stop, walk around her and make her stand still. After about a month we started to square her up during the leading lesson. We would walk about 4 or 5 steps, stop, square her up, stand then do it again. She knew how to stand for me walking around her head as if I was in a halter class and how to stand square before she was a year old. She took her first blue ribbon before she was one in an in-hand trail/halter class. She is 6 this year and will still square up when asked.