Having a strong recall can save your dogs life. If your dog were about to cross a street to chase a ball and you shouted "COME", would your dogs spin on a dime to return to you? Most owners answer no to this. I can't emphasize enough how important the cue "Come" is.
There are many training techniques I use to teach a dog to “come” when called some of my favorites are:
1) use a long line (first desensitize dog to it), use the running come game.
2) puppy come game
3) Doggie ping pong
4) Hide and seek
Don't forget that if your dog sees a ball, a squirrel, another dog...whatever the distraction may be, you need to think to yourself, "how can I be more rewarding than that ball, toys...etc"? What will make my dog want to choose me?
Find your best positive reinforcer and use it to train this cue. It may be a toy, it may be as simple as a good dose of praise!