The number one skill I would like people to master with their dogs is leash control. Often when folks join a class and we are discussing the things they hope their dog "learns" over the course of our seven weeks, their pup is demonstrating their out of control behavior even while they are on a leash. I place learns in quotes because I am usually much more concerned about what people learn rather than the dog.
Even if your pup is on a leash does not mean you have control of your fuzzy friend. If you are holding onto the handle and they are bouncing from one side to the other, wrapping around behind you, lunging toward others and essentially acting upon every impulse that they have, then they will not calm down. If their brain is constantly over stimulated then they have no chance of relaxing and focusing.
Shorten the leash so that they cannot reach others and cannot wrap around you. The leash should not be kept tight. If I am holding the leash as tight as I can and forcing them to stand right next to me then the dog is not controlling themselves, and will only spiral out of control the moment I am distracted. I will attempt to allow the leash to relax, and if the pup begins to pull or lunge again then I want to catch them on that first step, guiding them back next to me and allowing the leash to relax again. That first step is what I call the, "impulse step." If your pup gets three or four steps before I stop them, then they think they are getting closer to their distraction, and will try harder. Catch that first impulse, allow the leash to relax, and your pup will begin to control themselves much more quickly.