Before taking a dog in public or to an area where their are a lot of distractions; road or loud noises, other dogs, small animals, people, etc, it is imperative to classic condition them to a tug or treat. This refers to a learning process that occurs through associations between an environmental stimulus and a naturally occurring stimulus.
Begin training the SIT, COME, BACK and FOCUS in your backyard once this is 100% on and off leash move training to the front yard. Again, after you have the desired results both on and off leash move to an area in which there are limited distractions. I like and utilize parks or softball fields, during the week most parks do not have a lot of people, but tons of smells. I also like using stores like Lowes, they are dog friendly and you can find a quite corner to train for 10-15 minutes without being interrupted, this is really the first time you have introduced a strong distraction.
The more time you dedicate to train and to train with distractions the more your dog will start to recognize that when he is taken into public it is not a free for all, he is there to do a job and in order to get his reward he must do his part.
We must be the greatest reward to our pup, if the environment is more important we will never win.