Teaching your puppy to come when called is one of the most important lessons he can learn. A puppy that runs away when you approach may end up in the middle of the road, or lost, with no way to find his way home. The challenge with teaching your puppy to have a reliable recall is that many puppies view it as a game and will run away, hoping for a round of tag.
Keep him on a leash. Until you are confident your puppy will come to you immediately when you call, he needs to be on a leash when he is outside. A leash allows you to reinforce the fact that he needs to come to you when you call, not ignore you or run away. Each time he comes, whether he comes on his own or after you tug at the leash, praise him and reward him with a treat.
Practice the recall often. Practicing teaches your puppy to come when called, but it also encourages bonding. You call your puppy, he comes and you praise him. It is a great way to strengthen your relationship. Once your puppy has learned the basic idea of coming when called, attach a longer tracking lead or piece of clothesline to his collar so he can roam further away before you call him.
Use a fenced area to test your puppy. Once your puppy comes reliably when attached to a long lead, it is time to challenge him a bit. Let him loose in an enclosed area and allow him to explore. Once he is not paying attention to you, call him. Ideally, he will come immediately and you can reward him with treats and praise. If he doesn't come, don't keep calling him, either run the opposite way to attract his attention, or walk over to him and attach the leash. If you call him repeatedly without reinforcing the need for him to pay attention and come, he will learn he can ignore you.
Play games to reinforce the recall. If your puppy is coming when you call but likes to dawdle, or he stands and looks at you before deciding whether he should come or not, playing recall games may be all it takes to speed him up. Call your puppy, then take off running in the opposite direction or collapse on the ground and make sad, crying noises. Either will grab his attention and send him your way. When he comes over, reward him generously with treats and praise.