1. Be a tree. If your dog pulls on the leash, stop walking! Only continue walking once your dog has put slack in the leash. Consider a head halter or front-hook harness if your dog tends to pull.
2. Don't allow your dog to approach another dog without permission from the owner. Just because your dog is friendly, doesn't mean every dog is! If the other owner declines, don't get offended or try to force the other dog into a greeting. Remember, that the other dog may be recovering from surgery or an illness; he could be in training; or he may just have had a bad experience in the past.
3. Pick up after your dog. Not only is it unsightly and unpleasant to step in, dog waste is a source of pollution for surface water supplies, harboring pathogens like E. coli and giardia. So always pack some dog waste bags when you take a walk!
4. Barking at other dogs. Leash reactivity is a common problem among dogs that don't get enough mental stimulation or exercise. Try trick training and treat-dispensing toys along with longer and more frequent exercise sessions. Fetch, swimming, and running at the park are all great ways to supplement a daily walk.
5. Lunging and barking at passing cars, bikes, and skateboarders. This is often seen in herding breeds. The motion of the wheels can trigger a predator/prey response in your dog and incite him to chase. You can help this problem by redirecting your dog as soon as he notices a moving object. Create distance by moving away from the object. Redirect your dog with tasty treats and easy "tricks" like sit, down, shake, and following you as you walk backward.