This is something I've had to learn to do since I got a new puppy. My prior dog was an older dog and would not run up to strange dogs if I let her off leash. My puppy, on the other hand... I have to keep him on leash much more and when I do let him off leash I have to really keep an eye on him. Not a bad thing. Animals deserve to have engaged owners. I'm working on training him to leave other dogs alone when we are on walks. It is tough because he's so friendly.