The first thing I would do when taking the dog outside is tie a piece of thin rope about eight feet in length to my belt so that i can gently encourage them to come when I call. Also you want to make playing with you more interesting and fun than exploring the yard. Another recommendation is to when you say come then start to run away from the pup and they will chase you. When the pup arrives give lots of praise like they just won the lottery and they will start repeating.