First try to keep the dog on a leash short and not give it carte blanche to do what he or she wants. When the dog is in control so he can do what he wants and does not think he has to listen.
When the dog acts are not a big deal of it giving the dog attention. Continue to walk and give the dog a little tug to get his attention to the task ... being walked by you not the reverse.
Try to introduce your dog to other dogs when you are lucky and it seems safe. This way the dog walks are not the only time your dog sees them and it is not so serious. If a small dog play area in this city can be a very good thing for your dog.
The key to all this is not to react on the actions of the dog. You are the owner of the dog and as such should not let the dog see you panic on a regular basis. If all else fails then find a good dog trainer for assistance.