It is important to visit the dogs at the shelters yourself, even if the employees say there is no dog fitting the description. They are wrong sometimes. Change them immediately when you move. Be very careful to make sure the gates to your yard are always closed. Don't let anyone but your family have access to your yard.
Many people keep their gates locked.
Be careful that doors to the house are kept closed at all times. Some people have their pets micro-chipped or tatooed for extra protection.