One breeder of Newfoundlands noticed that one of her puppies had a tendency to carry things in her mouth, thus her name "Show Me". This trait is now seen not only in all of this bitch's puppies, but also into the third generation. 

Look at the sire and dam of the litter. Chances are (if you're buying from a good breeder) that you are buying a close copy of one or both of these animals.

During discussions of temperament, three words frequently pop up:

Dominant 

Dogs are pack animals, and each pack needs a leader.  Someone who establishes and enforces the rules. With any dog it's important that YOU, the human, assume the role of leader. If you aren't willing to be the leader, breeds that are dominant in temperament are more that willing to step into that position of leadership. As a matter of fact, dogs from dominant breeds will often challenge your position as leader, and try to "move up the chain" by challenging your spouse and children for their places within the pack.   

If you see that your favorite breed of dog is dominant and you have children living in your home under the age of 8-10, wait until your children are older to get this breed. You also must consider your children's temperament. The best owners for dominant breeds are confident leaders. "My house, my rules" or "Because I'm the mom/dad, and I said so" are their mottos. If your children share this strength and ability, then the dominant breed may indeed be the breed for you. If a timid or tender gene has slipped through the gene pool to one of your offspring, you'll want to consider getting a breed with a less dominant temperament. You can not have your dog thinking he/she ranks higher than any human member of your pack. For more information about dog behavior, see "Canine Behavior".

 

Balanced

These breeds don't covet the job of leader of the pack as much as the dominant breeds do. If you step in and fill the role of leader, these dogs will allow you to do so. You'll only find trouble if you don't take on the role of leader. The leader disciplines the pack members and keeps them in line. Dogs who are "balanced" will usually only step in to fill a void.

These dogs usually have the confidence necessary to withstand the "tender affections" of children in the family.  

Submissive

These breeds have absolutely no desire to be the leader. They'll readily accept anyone and everyone as holding a position higher than theirs in the pack. These dogs are best for families with small children and people who have never owned a dog before.   They make incredibly poor watchdogs and protectors and need an owner that is as tender and gentle as they are. Do not mistake timidity with submissiveness! A shy puppy who runs and hides is not submissive, he's timid. Such a puppy may respond to the children chasing after him to play by aggressively defending himself and biting.  

Keep in mind that there are submissive members of dominant breeds and vice versa. A good breeder doesn't produce submissive Akitas or dominant Shetland Sheepdogs. There are even various levels of submissiveness and dominance within litters!  

Make sure your breeder performs what is called a "temperament test" on the litter. This test will help the responsible breeder place the right puppy with the right family. One of the signs of a superb litter is where all the puppies test uniformly to the breed standard.