Some advice from a breeder:
One thing you should look for in your search for breeders and puppies, is a breeder who goes out of her way to rear confident, happy, courageous puppies. This is done by putting puppies through controlled, stressful situations, and making them overcome, think, try, and succeed. This is one of the biggest differences between breeders who are just "selling puppies" and those who are trying to create the best Golden Retrievers they can. Good breeders do this, the rest do not.
Our tongue-in-cheek mantra is, "Puppies must be abused!" In order to rear puppies who are not fearful, who are calm in stressful situations, who know their bodies well, and who have learned how to solve problems, it's important to put puppies in increasingly challenging, stressful (but safe!) situations where they have to problem-solve, and which gives them increasing confidence in themselves throughout the time they are with the breeder. We start doing that to puppies at Day 3, believe it or not.
Here's a super fun "agility" course we're going to do. Click Here for Video
This video isn't us, and we're going to be a little more careful about tiny puppies jumping and landing, but we are in the process of building something very much like this at our home for our Halloween litter. It will start small and change and grow every day until it winds up looking something like this. (I love the idea of Cavaletti for body awareness.) Your breeder may not go this far, but ask potential breeders what they do (if anything) to give their puppies confidence and to make them courageous problem solvers.
We do things like early neurological stimulation, adventure boxes, "woods" walks, slides, wobble boards, obstacle courses, and now this little puppy agility course. The challenges change almost every day. So every day the puppies have something new and stimulating, some new problems to solve, some new courage to work up, and some new game to play. We also teach puppies to follow their humans even when they have to overcome challenges to do it, and not to freak out in crates or when they are put in strange places, with strange people or animals.
Ask your potential breeders what they do to sell you a puppy that is confident, friendly, courageous, socialized, and knows his/her body. Such questions are one way telling one breeder from another, and shows breeders that you know a little something and aren't just out to snag "a puppy."
I usually like to start by saying something like, "We're interested in getting a puppy that is well socialized, has a lot of confidence in themselves, and knows their bodies well. Is there anything you do to try to rear confident, friendly, courageous problem solvers?" And see what they say. If they are like me, I light up at the chance for such a conversation, and I'll talk you ear off about it. OTOH, if they just give you a couple platitudes or excuses, then that tells you something about that breeder, too.