The sit position has practical applications, it is not just a trick. When walking the pup, you will find the sit useful at intersections, when meeting a friend, and in various other situations where you want the dog to be quiet and under control.
Start the lesson with the pup on the leash. You can place him on your left side; later he'll be walking or heeling from that position. Hold the leash in your right hand, give the command "Sit!" and lift up on the leash. This will raise the pup's head. With your left hand, push down on his rear end. Repeat these movements until the pup sits down without your having to lean on him. Then unsnap the leash and give the command. If he balks or sits down only halfway, put him back on the leash and start over. He'll soon learn that when he doesn't obey, he'll be restrained with the leash. Praise him well when he gets the lesson right.
Next, introduce him to the appropriate hand signal. Move a pace or two in front of the dog, give the command "Sit!" and hold up your forefinger in an admonishing gesture. Let him see it. Keep repeating the lesson, using both the command and the hand signal. While the hand signal has its best use when working at a distance, such as in the field, there are many situations in which you will find it useful. One of these is when there is too much noise for your dog to hear your voice.