I'm so excited for you! It thrills me that you are so enamored with them. Here are the things I think about, but the choice is yours. These are your Campines, and the selection according to your decisions is the essence of what makes them yours.
This line is strong in eye color. They are really dark, nearly black, and I have not seen any reddish colored eyes that other lines sometimes have. They also have far less than 50% red in the enamel white earlobes, in fact, most show no red until they are older. I have never seen white in the face of any of my birds at any age. Their leg color is excellent! I am so proud of the blue slate legs on these birds. I had a couple early on that had side sprigs in the combs and they were immediately culled as were the ones that were not hen feathered (had pointed hackles and side hangers in the saddle area.) Neither of these are common faults, but could pop up in the future. There are two different "intensities"of black in the barred areas. Some birds, mostly females, are more of a dark charcoal gray and the males like them have less of the beetle green they need. I still use them for two reasons - one, it is acceptable for show and - two, they tend to be the larger birds. I prefer the others who are darker black with plenty of the beetle green sheen, but that size is important. I would like to eventually breed out the gray gene, but not until the size is right. I don't worry about any of these qualities (mentioned in this paragraph) because they are consistently good, but if a bird had issues in any of these areas, I would not use it for breeding.
First, and foremost, cull ruthlessly for vigor and type. If any of yours are weak, sickly, or not as active as they should be, don't breed them. As to type, read the first 40 pages of the Standard (Great decision on buying one, it is a good investment) at least three times through, studying it and committing it to memory. Then read it again and often. I look for a rounded breast, carried well forward (VFS - viewed from the side.) I want a straight back that slopes slightly toward the tail (VFS.) I also look for a broad back from the neck to the hipbones (VFT - viewed from the top). I like plenty of room between straight legs (VFF.)
An old timer told me that you get your color from your cock and your size from your hen.
That says to me that I should put more weight on markings on the rooster as long as vigor and type are there. For the cock, I want clear, white hackles. So far, all of mine show at least some black in the hackles once they get to a year old and I find that it increases as they get older. If he shows yellowish coloring in his hackles, he is likely "split to Golden" or carries the recessive gold gene. That is not bad for a breeder, but doesn't show as well. Next, I want to see the barring on his chest go as high up the front of his neck as possible with the goal being all the way to the throat. So far, I have found that the higher it goes, the more black in the hackles. That is a constant balancing act. I am working on getting barring on all the tail feathers and limiting the white in the primary wing feathers. I had a man at the Newnan show tell me they are supposed to have all black on the central tail feathers. He was wrong. I like a broad head (VFT) and, although the judges' score card doesn't put a lot of emphasis on combs, I think the comb is an important element of the aesthetics of the cock. I am not so concerned with the number of points, but more that it is not too big and is uniform. I'm looking for clean barring. The white stripes are supposed to form concentric rings around the body. I doubt that will be attained any time soon, but I have seen some decent patches of good barring which makes me optimistic.
Check those larger girls and make sure they don't have any DQs, or are lacking in basic type and then USE them! Like the males, I want to see clear white hackles (FYI, girls will always be pure for either the silver gene or the golden gene, they cannot carry both.) Once they reach POL, I look at egg color (the whiter the better,) and the spread in the pelvic bones (EIH - evaluated in hand.)
Handle your birds often. Get in the habit of picking them up and keeping a check on their weight, bone quality, and condition. They should FEEL heavy in your hand and should be well fleshed.
I had to cut this short........ I can talk about this all day long!