Sit is the first command your puppy should be learned. And its pretty easy too, as you will se in this video. Andy got it at 8 weeks of age and after two days of training. All you need to do is hold treat close to dogs nose and slowly move your hand up and back to your dog so he will naturally sit. When he got to the sitting position say „Sit“.
At the beginning, always show your dog affection and give give him treat, after he will sit, but never give him a treat, if he does not. As always, patience and consistency is the key, never push your dog to the sit position. After your dog will master this command, ask your dog to sit before meal or before leaving for walk. You can also add some distraction or start doing this command without treat.
This is how i trained my dog to sit: