Sit is a good starting point for training your pet. The sit command is simple to teach and is a good command for your dog to know. Sit can end a lot of behavioral problems your dog can develop such as jumping up on people, running away when they are outside, and running outside when you open your door. Sit is also good to teach your dog because lots of other commands can be taught from the sitting position.
This technique requires your dog to have on a collar. Kneel in front of your dog and face them. Have a treat handy, either in your pocket or close by, but not in your hands. (You are going to use both your hands for this technique and if you are waving a treat around your dog's head it can be distracting.) Constantly repeat the word "sit." Take one hand and place it on the rear side of your dog's back. Your hand should be positioned in the center of the dog's lower back between its hips. Take your other hand and grab the dog's collar over the top of their head. Simultaneously push down on the dog's rear and pull up on the collar. This will make the dog sit. You don't have to be too forceful; just do it hard enough for the dog to sit (you don't want to hurt them). Once the dog sits, keep repeating "sit," and tell the dog they did a good job. Reward your dog with a treat and give it love and affection.
Repeat this process several times, repeating the word "sit" or whatever trigger word you have chosen. After several attempts your dog should begin to sit on command without having to be forced. The use of the word "sit" should begin to be sufficient by itself. Continue giving your dog treats and love every time you get them to sit. If this technique does not work, don't worry there are other ways you can teach your dog to sit.