My dog trainer said the best way is to pull the dog back to where you want it to walk and exclaim forcefully Heel, then praise her while she is doing it correctly. A small treat for doing what you ask initially is useful, then trade he verbal praise for her good behavior. Constant (daily) reinforcement of the behavior is required. Even when I went 8-10 months without walking her (after installing a doggie door so we no longer had to walk) she initially pulled a little ahead but a pull back and the heel command got her back under control quickly. I hope this helps, it worked well with my dog, I hope it works for yours, too.

My 7 year old Shih-Poo shows her displeasure at being left alone by peeing on the dining room rug. She has a doggie door, so it is not that she had to go indoors. It does not happen every time, but often enough that it is a problem. Since it is a black rug I cannot always tell by looking that she did it. Often the only way I knew she did it was stepping in cold pee. How do you train against this behavior?