Pair your recall word (example: "come" or "here") with your dog's favorite reats and toys.
Say your recall word as your dog is coming to you.
Always use a happy, high pitched tone when calling your dog.
Don't call your dog to come for things he finds unpleasant (punishment, nail trims, bathing, crating, ect.). Instead go to him or play a short game with him first to separate his coming to you with the unpleasant thing.
Never punish your dog for coming to you, even if it takes him a long time to get to you after you call him....you would be punishing him for coming to you, in his mind.
If your dog gets distracted on his way to you, clap your hands and make happy sounds while running in the opposite direction.
Always reward your dog for coming to you and vary the rewards you offer.