There's no one-size-fits-all solution when it comes to making sure that two dogs get along with one another. You have to consider who they are individually, together their environments, past experiences and how they feel towards one another as a whole. But there are a few things you can do to help encourage a positive and safe introduction. 1. Safety first. Make sure that you use space, as well as a leash on both dogs to be able to maintain a safe distance for both dogs. This isn't only to prevent any potential physical altercation, but also to help both dogs feel like they have space and time to think their thoughts and decisions through and above all walk away if they feel unsure about the overall interaction. 2. Ensure both dog's minds and bodies are as relaxed as possible before meeting. Though you don't want to have either dog feeling overly tired, you should still provide both with fun games and activities prior to the meeting. This will help both dogs feel good about themselves while also encouraging a calmer and more mellow demeanour during the introduction.
3. Avoid meeting face to face and pick a neutral environment. You're more likely to be successful if you have both dogs know of each other in an open, neutral space, especially somewhere where they can do activity at a safe distance from each other. For example, an open park where one dog is playing ball with their handler, while the other dog is snuffling for treats with their handler. From there, you can slowly get closer to one another and see how each dog feels. No matter what, do make sure that you keep the interactions short and sweet! This will leave both dogs feeling like nothing bad happened, and like they could do this again.