The sit is perhaps the most useful command in your obedience repertoire. Putting your shepherd on a sit when someone is coming in the front door gives you more control over the situation. Requiring your shepherd to sit while you prepare her dinner is much more convenient than trying to navigate around a dancing shepherd in the kitchen. If your shepherd is in a sit when you put the bowl down, you won't have the bowl knocked out of your hands. Putting your shepherd in a sit is also a convenient way to keep control of the large dog around small children and frail adults.
The shepherd learns quickly, which means he will learn both correct behaviors and incorrect behaviors rapidly. As his trainer, you need to be aware of exactly what you are teaching him. If you click at the wrong time on the sit, she could learn that the command “Sit” means crouching on the way to a sit. Training the skill correctly the first time is much easier than trying to fix an incorrectly taught skill.
If you are using free shaping to teach the sit, you'll need to carry your clicker and treats with you around the house. Every time she sits, say “Sit!” and immediately click and reward. When she seems to have made the connection between the command and the sit, give the command “Sit!” as she is beginning to sit. When her rump hits the floor, click and reward.
When she performs this correctly at least eleven out of twelve times, give the command “Sit!” when she is looking at you and making eye contact — but not preparing to sit. Continue to add variables, such as distance, initial positioning (such as when she's already in a down or standing), and movement (when she's walking or standing still).
The sit is also frequently taught using a food lure. Stand facing your shepherd, and gently hold her collar with your left hand to keep her in front of you. Hold a treat in your right hand. Starting at her nose, slowly move the treat (fingers down and wrapped around the treat) above her muzzle and over her head. Your fingers should nearly touch her as your hand moves over her head toward her back.
This lure movement will cause your shepherd to rock back on her haunches. As soon as she plants herself, say “Sit!” click and reward. Repeat this at least twelve times or until she is easily moving into the sit as the lure is moved over her head.
Don't be surprised if your shepherd begins sitting when she would like a treat. She may also glance back and forth between you and the treat jar to initiate a quick training session. This is okay — shepherds love to perform for their humans. Just be sure that you ultimately remain in control.
Next, give the command “Sit!” as she is rocking back with the movement of the food lure. As soon as she sits, click and reward. When she is consistent at this skill level, give the command when you are holding the treat. She should sit. If she does, click and reward. If she doesn't sit, go back to giving the command while moving the food lure over her head. Work until she is completing this correctly eleven out of twelve times.