1. If possible, plan to introduce your dog to potential new buddies on neutral territory, like during a short walk through your neighborhood, in a nearby park or in a friend’s yard.
2. To minimize tension, try to keep the two dogs’ leashes loose so that they’re not choking or feeling pressure on their necks.
3. Don’t force the dogs to interact. If they try to avoid each other, or if they sniff and then try to go their separate ways, let them. Let them investigate each other on their own time.
4. If they show no interest, try again on another day. If the dogs avoid interacting you’re you try again, they probably aren’t the best match.
5. Make greetings positive and light-hearted. As the dogs sniff and get acquainted, encourage them in a happy tone of voice. At first, allow just a few seconds of sniffing, and then gently pull them away for a minute. Lead the dogs back together and allow another several seconds of sniffing. These brief sessions will help keep the dogs’ interactions calm and prevent escalation to threats or aggression.
6. You can also break up interactions by asking your dog to do some simple obedience, like sit and down, and give her treats for her good behaviors.
7. Closely observe the dogs’ body language. Their postures can help you understand what they’re feeling and whether things are going well or heading south. Loose body movement and muscles, relaxed open mouths and play bows are all good signs that the two dogs are feeling comfortable. Stiff, slow body movement, stiff mouths or teeth-baring, growls and prolonged staring are all signs that a dog is feeling threatened or aggressive.
8. If you see this type of body language, quickly lead the dogs apart to give them more distance from each other. They probably don’t want to be playmates.
9. Once the dogs’ greeting behaviors have tapered off and they appear to be relaxed around each other or excited to play, you can take them on a brief walk together.
10. If all goes well, take them to a safe, secure area where they can run off-leash.
Source: aspca.org