In my opinion, the single most important thing that a breeder can do for their pups is to raise them properly. Within this statement though, please take it as a given that the breeder has already attempted to line the genetics up as well as possible to produce a strong puppy in regards to both physical and mental health. This in turn make our job of socializing and training as fun and easy as possible.
That said, here are some ideas for rearing a happy, well-adjusted pup:
During the first 1-2 weeks, touch them and talk with them. All the time. A million times a day. Sit/Lie right in the whelping box with them. Every time you look in on puppies from day one, each one should be stroked and talked to. You'll be amazed at how young they are when they start to look forward to this and pull themselves toward you for attention. Touch them all over, on the face, on their feet, rub their tummies and armpits. Hold them close to your neck and face so that they get used to the warmth and smell. No matter what else you do for your young pups, nothing is a better substitute than the human touch.
Also, utilize the early stimulation techniques. The theory behind it is that small stresses boost the immune system. Go a step further and move the pups around the house a bit, even when they are very young. Every room has it's own smells, every surface a new feel. Each day, put something new into the whelping box for them to explore. You'll be surprised how creative you can get when you have to find something new every day for 9 weeks ;)
Once they're very mobile, say 3-4 weeks, start letting them out of the box to explore the world. Get them onto every imaginable footing and outside into grass or snow for brief periods. Nothing is sadder to me than an adolescent dog that can't manuever a slippery floor, or can't walk over grating. It tells me that the breeder did nothing with them when they were young. Now's the time to start adding really fun stuff to the puppy playpen. Logs for them to crawl over, a tunnel to go through, a small tire to go in and out of etc. They want to explore and will take every opportunity. Also use this time to introuce them to new sounds. The tv, the dishwasher, the vacuum, etc.
Around 5-6 weeks, the fun really begins. Go for walks in the woods, introduce them to swimming (a baby pool outside in the summer, the bathtub in the winter), get them on the agility obstacles, and incorporate items to be carried (sticks, dowels, small dumbells etc.). Start letting them interact with other adult dogs in the house that you know will be good with them. And invite every neighboring child within a 10 mile radius to come and play with puppies.
This age is also the time to start firming up behaviors. Take them out one by one and reward for eye contact, coming when called, retrieving. Start to teach them to trade an item in their mouth for a treat. Use a food lure to manipulate their bodies so they learn to move sideways and backward, not just forward or up. Start taking them outside to potty, and again, a reward for a good job done.
At 7 weeks, do their PAT test or whatever test you use. We use the Volhard test, and also add about 20 more items of our own that assess ability to problem solve, work through stress etc. Once you're confident that you know what each pup has, or is lacking, you can use the time left with them to work on what they need, or strenthen even further what they already have.
At 7-8 weeks, it's time to be on the move. Go for car rides. Take them into the stores and post office with you. Take one to the hairdressers, or the gym. You'll be amazed at how welcome your pups will be, especially if you only have one or two at a time. Simply explain that you are working to socialize the pup so it will be a better dog for it's new owner, and you'll have everyone you encounter willing to help. In fact, I'd be surprised if their feet ever hit the floor when they're out in public
Go out of your way to find new sights, sounds and smells for them at this age. Drive through the car wash, take them into McDonalds, basically just go about your day, but take a puppy along. If you have kids, take them to visit their school. If you're training other dogs, take the pups with you. Also, start tracking now and working with a soft rag/tug if the new owner is hoping to move on in these sports.
Then, send them home to the perfect new home that you picked out just for them, based on what you've learned in your interactions, and watch them succeed!
Ann