Age Matters
Play styles can vary greatly between a young puppy and a seasoned adult dog. Young puppies tend to like energetic, rambunctious play, so they are best suited to play with one another. In contrast, an older dog might find this frenzied kind of play to be irritating. In addition, older dogs can be choosier about their playmates, so be patient as you and your dog find your way to the right canine friend.
Evenly Matched
Your dog and her playmates should be relatively similar in size and build to prevent any accidental injuries. Not surprisingly, smaller dogs are prone to getting injured when paired with a large breed of dog. They can be stepped on, knocked around or simply overwhelmed. Keep your dog happy by finding another pooch she can let loose with, without injuring or being injured.
Dogs of a Feather...

Let Them Have Their Say
Ultimately, let the dogs decide whether they want to be friends. You wouldn't want someone else choosing your friends, would you? If your dog and a potential playmate seem to have no interest in one another, they may simply be ill-suited as playmates. But if your dog displays regular excitement in playing with another dog, it probably means you have succeeded in finding the perfect doggie playmate!