The main caution that I always stress and it's really important is: Don't ever call your dog to come...don't use the command UNLESS you can be positive that he will come or that you can enforce it. Your calling and calling him has taught him that he doesn't have to come when he's called. Like bubbatd said, go back to the leash. If he's not on the leash, don't use the "come" command. Entice him with craziness, fun, silly, play, running the other way, hiding behind a tree making squeeling noises. Then when he comes and he's running toward you, squat down with your arms open, giggling with fun and when he is 2 steps away and OBVIOUSLY coming, say, "COME" and then praise him..."gooooooooood come!" And DO give him a super wonderful treat...not some dried up dog biscuit. Use something he LOVES....cheese, homemade treats, a piece of meat. Otherwise, practice with a long line....do the same thing. You can help him to come with that, but still make it fun. Make coming to you better than anything else he's interested in at the time. Get it to be a habit. It will take a really long time and a lot of training until you can trust him to come every time, reliably.