This is an interesting topic actually, because I think everyone wants to be able to magically "know" which are going to be the best pups in their litters. However, when you're a breeder, and while individual superiority is a reality, the real goal should be to produce a litter where every pup is a standout in some way (or, better yet, in the same way you've bred for). In fact, it could properly be said that the easier it is to choose which pup you want from the litter, the worse your breeding is (because the majority are undesirable), whereas the harder it is to decide which pup is best in the litter, the better your overall breeding is (because each littermate stands out in its own way--or, better still, in the same key way).
I mean, after all, if we're breeding for specific traits, the more pups that display the "stamp" of these traits the better the overall litter is ... while the fewer pups that display this "stamp" the more you missed the bullseye (or even the whole target) in your breeding effort.
Well, I am glad you gave me license to take this post in the direction I want, because the first things I look for (soundness/movement) weren't even on your list ... so I took the liberty of adding them
IMO, soundness/vigor is different from mere "conformation." For example, you can have a dog with a fine silhouette, and by that I mean pleasing lines, but it just doesn't *BEAM* with vitality or vigor. This is a BRUTAL business we're in, and so to prevail in what may be a 1-, 2-, or 3-hour contest that MF has to have some pizzazz to his ass. He has got to be be FULL OF LIFE, VIGOROUS. And the other thing he needs to do right is move with speed, balance, and precision.
So, to me, it is impossible to pick "just one" thing I look for ... instead, I will say that the first things I look for are soundness/vigor and the way the pup moves. After that, it is intelligence and alertness.
It's only a "gamble" if you don't know what you're doing ... because if you really do have a good eye and selection protocol, why then you're stacking the deck (or counting cards) aren't you?
Well here again though, the better your breeding, the more pups in the litter you'll see having the traits you want ... whereas the worse the breeding, the less pups you'll see exhibiting the traits that you want. The best breedings are those where you can "pick any pup" and have a good shot at getting a damned good bulldog ... whereas the more only "one" pup stands out as a vigorous athlete, while the rest are sulled-up discards (or slow, lumbering oafs), the lousier the breeding is as a whole. (IMO, most litters are full of slow, unathletic slugs.)
What you need to do is determine what you want most out of your dogs, establish a pattern or "signs" in the dogs of your family which carry these traits, and then learn to "see" these signs (or "stamps") in your pups. However, the only way to be able to do this is with a family breeding program ... no way in hell can a person do this if he's "crossing this to that" all the time ...
There's mine
Jack