In my experience dogs are more likely to accept another dog if the dogs are walked together rather than having a face-to-face meeting in a backyard. Also if you do use a yard make sure it is ‘neutral territory’ so to speak. If you bring one dog into the other dog’s yard they may get territorial. If the new dog has issues with other dogs, you can also check if there are any classes for dogs with this problem in your area. Many times you can find a training class which is specifically for dogs who have issues with other dogs. These classes have names like Reactive Dog Class, Reactive Rover, Growl Class, Charm School, etc.