Learning the Sit command is important for a number of reasons. For one, it allows you to control your dog in a situation where they might get hurt if they do not stay where they are. It is also a good command to help stimulate your dog mentally. By nature dogs love to please, and they seek leadership, by going through the sit command on a daily basis you are providing your dog with leadership and stimulating them mentally.
In order to train your dog you need to mentally prepare yourself by being, calm, and assertive. Our dogs read our emotions and sense our weaknesses, unless you can demonstrate yourself as leader do not expect your dog or puppy to listen to you. Sit is one of the easier commands to teach, and usually the first one that you should teach.
Grab a handful of your dogs favourite treats and take your dog to a quiet place where the two of you can work with little or no distractions. Hold a treat in your fingertips and put it above your dogs head and say "sit" in a calm, firm voice.
No matter what your dog does, do not give him the treat until he sits. Sometimes you may need to bring the treat over his head mid-body, so that when he follows the treat with his eyes he puts his body into the sitting position to see the treat.
At the first moment your dogs behind hits the ground say "Good Girl/Boy," and give them the treat. Repeat this exercise several times until your dog sits each and everytime upon hearing the word.
Some dogs learn this on the first day. Others may take a few days of practice. Limit the training sessions to 10 minutes, you do not want to bore the dog, and do a few sessions each day. The goal is to keep them mentally stimulated.
After a while, once your dog has successfully sat down each time with a treat in your hand try asking your dog to sit without the treat.
If they do not sit, put the treat in your hand and repeat. However, this time when they do sit do not give them the treat, simply offer up praise, and affection.
Then the next time you say "sit", give them the treat. Making treat giving random. This will make your dog more likely to comply as he/she will not know when they will receive a treat for obeying, and it makes the training that much more intriguing for them.
You can practise getting your dog to sit outside while on walks or just in the garden. Having your dog sit on command is great for you and your dog.