I have some strict criteria in thinking about breeding as well. Like Beau said, the mare and stallion both have to be proven, so no stallions that are bred just because the look a certain way, but have never actually done anything themselves. Conformation has to compliment each other, and improve upon each other, just because some stallion may shorten the back of a mare who is a bit longer than ideal does not mean that it will actually be improving as a whole upon both parents. Hopefully you understood that. Both mare and stallion have to have a likeable personality, and have to enjoy being worked. No bad attitudes even if the horse can jump the moon, I wouldn't breed if the horse just looked upset, mean and nasty while being ridden. If I buy a mare for breeding, who's already been bred, she'd better have thrown a nice baby or two or three, from decent stallions, and same with the stallion, he has to have some good looking foals or foals that have achieved things themselves with similar crosses to my mare before I'd consider breeding. To me, there are only two reasons why you should be breeding, either to better the breed(s) you are breeding, and create hopefully outstanding foals, or as in the case of some ranches, breeding for nice strong working horses, that can keep a ranch going. I don't class breeding ranch horses under improving upon the breed, because a lot of them are just looking for a nice level headed cowy horse that can work all day, has good bone and good muscling, but isn't necessarily the "ideal" of the breed registry.