Dogs are pack animals and thus social by nature. However, just as with people, some dogs socialize better than others. Some dogs even have problems socializing with the other sex (That sounds human!). Still considering that dog are pack animals it is weird that some dogs find it difficult to get acquainted to other dogs.
Dog owners often have other dogs and pets visiting or living with them. To make sure all animals live peacefully together is not something that happens on its own. When on top of that your neighbours' dog visits your premises every now and again and the ocasional cat wandering through the garden, you better be prepared.
To prevent potential problems you better prepare your dog by socializing him as soon as possible. When dogs grow up, very much like adults, it's more difficult for them to learn the rules of social behavior. It's very important to expose your dog at the earliest age possible to other people and dogs. When they are still puppies the whole world is new and wonderful and they are very open to new experiences.
When your puppy has received all his vaccines it time to meet other dogs and people. It is important that many different people touch him especially in sensitive places like ears, toes and close to the eyes. This will make the visit to the vet much easier. Off course he needs to meet as many other dogs and animals as possible.
Dogs like to sniff each other. When they're about to meet another dog you should control the set until you're confident that both dogs won't start fighting. Only after that you can let them explore the other dog.
If your puppy likes to jump on or bite other dogs, see if the other dog corrects him in a gentle dog manner. You should only interfere when one of the dogs is at the point of getting injured. Just stay near your puppy for an emergency intervention, just in case. You might want to bring a pair of gloves if you expect fighting.
Sometimes they start barking which can be annoying. You can try to make him stop by giving him a treat or give him his favorite squeeky toy. If that doesn't help, just go home and come back the following day. You'll have to learn what works best for your dog, because each dog is different when it comes to behaving around other dogs. Just take your time and learn how your dogs socializes best.
If you have a (adult) dog that comes from a rescue shelter and you don't know his past you might need more time to teach him proper dog behavior. Many of these type of dogs have had bad experiences in the past and it might take them some more time to trust other dogs and humans again. They might be violent or shy, but whatever the way they react, bear in mind that many of these dogs turn in to wonderfully adapted animals with a little bit of love from their owners.
With socializing it is very important to begin as soon as possible. Expose your puppy to as many other dogs as possible and you'll have a perfectly socially adapted dog.