First ,You must know what it the best "time (meaning age wise) as to which are the "show, "companion" and "breedable bitches " and those boys that  are the quality needed to be a good, top quality Show ,Stud Dog (These seem to be few and far between in the past few years -
unfortunately).

Knowing  the bloodlines is a MUST ,in order to know how they grow and at what ages , they have their growth spurts. This good be spurts in bad and good directions. Puppies grow at different growth rates.  Certain bloodlines look great at one age, while others take a younger or older age when they look their best or worst.

My own personal thoughts on how we choose out "show" quality ,is that we watch them at about 6 weeks of age and there are always those that "stand -out ". If the overall litter looks good ,but your eye tends to go to a certain one or two, it -pretty ascertain that those most likely going to hold. 

In NO way do we choose at 6 weeks, we watch about every other week after that, changes seem to really take place at two week intervals. Sometimes, those ones that "stood out",  have been joined by maybe one or more puppies, to be an :"eye catcher ".  Sometimes, again those from 6 weeks ,that caught your eye , are still catching your eye!  We really don't get serious about who will be chosen (that we think at that time) until around 9 weeks of age. As I said , that every bloodline has it differences in growth. Our bloodlines .definitely have those times .
It seems to be a slow growing ,maturing bloodline. Meaning, again that as time goes they just get better ,if they started out good , or some that you may have thought ."weren't all that " seem to "come-on" at about 9 - 10 weeks of age.

This can only make it more difficult to choose as more have joined the "show" "keepers" group.

Any male puppies that don't have both testicles by 9 weeks are sold into "companion" homes on a neuter contract . As we have been told and also experienced - in the monorchids that we have had (which I will add are few! very -few) IF they don't have them both down and descended  into the scrotum at that age, it VERY rare that they will ever be there.

The age of 10 weeks NO one leaves as in the behavior readings - this is a very traumatic age for puppies to be moved ,into any different surroundings, and this is the age when they really need the security. Seems that after that week and at 16 weeks again -another trauma time for behavior .

So, our rule of thumb is , we do not send out any show prospects "before" the age of 16 weeks and 20 weeks.
We make out final decisions at 15 weeks of age . This has proven to be the best age to finally point and say ,which category each one belongs in ,according to past breedings, and the bloodlines involved.

At this age of 15 -16 weeks of age , you can see the movement, the temperament,  and what sort of personality each one has, along with strong points, and weak points (that need to be worked on). Also, at this age, puppies have been thru their series of the most needed vaccinations, and wormings, the crucial ones before they are placed into their *new* homes. Thereby having the antibodies needed in their systems.

It is also a good time to be sure to check for correct bites, or what the condition of the bite is at that age . 

Angulation , and movement,  character and personality, along with temperaments , should be very apparent at this age .

Our words to prospective "show" puppies, "we do not sell any of those until and between the ages of 16 to 20 weeks of age ". This way we know for sure (well in many areas for sure) the quality of the puppy, and it also is old enough to get an idea of the hip and elbow status as well by having them prelimbed.

On all of our litters , we plan to keep only one for ourselves, however there have been times when we have kept two,  just because it's hard to get the good ones . If we decide to keep two in  a litter , a lot of times it is because the bloodlines are so goo, and we keep maybe one bitch to show and the other to breed .This way when the show bitch finishes her Championship (hopefully), the other sister already is well on the way to producing puppies to try to achieve an ROM. As most show bitches don't even get bred until the age of three (3), because of being in the show ring , and waiting for them to mature.

The stud dog world is a tough one - So we plan to just enjoy this guy Royce !!

So that is it for now -on how we choose ,and at what age and what we look for when selecting our puppies ...

I will probably do more on this subject .... to be added later .. and Thanks Zoe for asking me to do this -- I enjoyed it!