Recall is one of the most important things you should teach your dog! You have to be more exciting than an exciting and busy world. Start in the house, then move to a quiet yard and then to a busier area. High value food is key as is a happy voice and your moving away from them to include a bit of chace. TIP- shelter dogs sometimes have a negative association with the word "Come!" as it may have been used in a bad way. Choosing an unusual recall phrase like "Here boy" or "Fine me!" may be more beneficial to layer in fun.