It's quite common for dogs to become averse to certain things. Occasionally the aversions turn into full-blown fears or fear-based aggression. It's not fun for your dog, and it's not fun for the dog owner. Exposing your dog to many things from an early age can help to prevent this problem. Some common things you will want to expose your puppy to include:
* People - men, women, children, babies
* Other dogs
* Cats and other animals
* Riding in cars
* Going to the vet
* Nail clipping
* Stairs (including ones you can see through)
* Being alone
* Loud noises including fireworks and thunder
* Bicycles, skateboards, scooters
* Public places and crowds
* Walking on a leash
When exposing your dog to these things, it's important to make it a positive experience. For instance, you might give Fido his favorite treat or give him a massage while you clip his nails so that he thinks of nail clipping as a happy event. If Fido is naturally fearful of certain things from the get go, you will want to introduce him to those things slowly or in increments.
It's especially important for puppies to be socialized with other dogs and people (strangers). Puppies go through a critical period of socialization between 1 to 4 months of age. If isolated from the outside world during that time, they can grow up to be unbalanced adult dogs. Some veterinarians advise people to keep their puppies in the yard or home until the entire vaccination series are complete. Of course, you should complete the first set of vaccines and keep your pup away from high-risk areas, but did you know that the chance of a dog being euthanized for behavioral problems is 1000 times higher than a dog getting sick from parvovirus or distemper?
It's also true that dogs, especially young ones, can be easily traumatized by a single negative experience with another dog. So it's very important that you monitor your dog's interactions with other dogs, and that you don't put your dog in a position where he has to defend himself. Dog parks are great, but as your dog's guardian, it's a good idea to educate yourself on subtle dog behaviors and always keep an eye on your dog, so that you can prevent bullying and fighting.
It's always easier to take precautionary measures to prevent fear, than to counter-condition a dog that has developed a negative emotional response towards something. Trust me on this one - early socialization is well worth your time!