A reliable COME command can save a dog's life. It is essential for many reasons that D comes when you ask, and come immediately. In the dog trialing world, therefore, a reliable come is one of the things regularly tested for to obtain a Qualifying Score. In agility, "come" or "here" is what helps bring D back on track if they misread your body language or the next obstacle command. Handlers whose dogs go trotting off sniffing some scent or run out of the ring to visit a bystander, don't have a reliable enough "come" command.
The payoff for coming on command has to be bigger than the payoff for not coming. In Susan Garrett vocabulary, you must "build value into the desired behavior".
My Definition of COME: Whatever D is doing, they quit doing it and come immediately to you and stay by you until released. Control of your D can include grabbing their collar, putting a leash on them, having a reliable sit/stay at your feet or at your side, telling them to crate up or get in the car or house).
TRAINING: To train a reliable and immediate "come" with ease, get a whole bunch of high value treats (tuna, cheese, hot dogs, tasty crackers) in your pocket and keep them there all day for several days. Start with your puppy. At random moments throughout the day, (starting close by but eventually across the yard and from different rooms) say
DOG'S NAME/COME . . . . . . . Maxie, come!
Encourage them to come by patting your leg and making eye contact. The exact moment they get to you, pat their head, hook their collar and ply them with a generous treat, and generous praise. Say "Good come". (Not "good dog".) Pet D and show your excitement that they listened. Pick them up, whirl them around, etc. Then release them. "Okay, go play."
Vary, and gradually fade out the treats, the praise and the petting, and encourage them to just come and sit quietly in heel position or directly in front of you until they are released.
At various intervals, as they sit you should also clip on their leash or slip one over their heads, then treat generously. "Good come. Good sit." Throughout their life, D should show NO resistance to being put on leash, so training both the come command and leash acceptance simultaneously is efficient and makes sense.
Reinforcement: Throughout D's life, at unpredictable moments, give D a really nice treat for coming. Never forget to reinforce good behavior periodically, or suffer the consequences of taking things for granted. We all know what happens to the ungrateful wretches of this world!
GROUP "COME" EXERCISE: I have 4 dogs. I line them all up in a sit//stay. I leave the room and go around a corner. Willow follows me as she will not sit/stay for anything. The others stay. I say "Maxie, Come", and Maxie races to me for a treat. I say "Lucky, Come", and Lucky rip roars to me for a treat. I say "FoohFooh, Come", and he comes for a treat. I sit them all again, go back to where they originally were, and call them again, changing the order. If they come without being called, and at first they do -- they get nothing -- no treat, no acknowledgment, no fussing at them. I don't even notice them until it's time to start the next round. Within short order, they are waiting to hear their name called before leaving their spot. Sometimes I wait a whole minute before calling the first name. They think this is such great fun they are wriggling with excitement, eyes beaming, intently focused. Because of their enthusiasm and my growing confidence that I can control them if it becomes really necessary, I think it's fun too.