Sharing your life with a great dog is a lot like any important relationship. Social skills matter. Behavioral research understands this. Puppies do better in life if they stay with their mothers and litter mates until the age of 5-7 weeks.
Picking the right breed is important too but remember that everybody is a unique individual; puppies aren’t appliances that roll off an assembly line. You’ll want to pay attention to the variation in temperament within each litter. I recommend first choosing the racy appearance of your shiny new dog. Then close the book on that breed and carefully sort through the applicants.