The only generality worth noting is that unneutered male dogs bite people the most. Neuter your dog. The best sources for a good pet are reputable breeders, word of mouth, rescue groups, and animal shelters. A bad breeder sells you a puppy with few questions asked. A bad breeder always seems to have puppies, often breeding four or more litters a year.
Good breeders know their dogs.
You'll be able to meet at least one of the pup's parents and should like the parent. The apple does not usually fall far from the tree with dogs, and if your potential pup's mother is too protective, nervous, or whatever for you to meet and handle, skip her pups. You want a friendly, outgoing, stable pet, and those come most often from friendly, stable, outgoing parents. Word of Mouth People move, schedules change, and good dogs need new homes. Resist the temptation to rush.