With the buckle collar and a 6 foot leash attached, have the pup sitting at the heel position. Take a piece of food the pup likes in your right hand. Kneel by the pup - getting on his level. With your left hand, hold the collar above the shoulders and your arm lightly resting along its back.
Show the food to the pup directly in front of its nose. Say 'DOWN' and lower the food to the ground between and in front of its front paws. If the pup is long/tall, you will have to put the food further in front to allow the body to stretch out straight. Hold the collar only to maintain control. Do not push or pull. When the pup is down, immediately give it the food. Praise and pet it calmly to keep the pup laying down. Give the release word 'OK' or whatever you use and allow the pup up.
Repeat often. Teach only the down command until it is learned. Later, you may teach the pup to sit from this position. Just work opposite the down requirements, moving the food up to where the head will be when it sits up and say 'SIT', giving the food when it does.
Soon you won't need to touch the collar at all. As the pup progresses, begin working further away from it. Just make sure you make the pup do the command quickly. Do not repeat commands hoping the pup will do them because you know it knows them. That is exactly why you don't repeat, but enforce and reinforce the desired behavior.
The signal is the open right hand, with palm towards dogs' nose, swung down from above the dogs' head down past his face and towards the ground, when you are standing at heel position with him. The use of the food in the moving hand whilst training helps get the pup used to what will eventually be this signal. If you teach the signal from in front of the dog and facing him, the usual method is to raise the right hand straight up to its highest level and then bring it down either in a swinging motion toward the dog then to your hip or drop the hand straight down without swinging. The swinging is useful in that it can be helpful with correcting the dog by hitting the leash when it is held taut in the left hand.
