I will show you how to train a dog to sit, say down, stay, and come! It works with all my dogs, why not yours?

Step 1: Sit

first notice that i have nothing in my hand. that is preferably the main thing.
To train your dog sit, hold your hand out like you have a treat in your hand and say sit.
if done correctly, your dog should sit.
Note: It may take some time so don't get frustrated.

Step 2: Lay Down

This is a little harder for your dog. Still, have no treat in your hand. Do sit and after that put your hand all the way down and say lay.
Maybe it is a little easier.
Note: this will take more time then sit.

Step 3: Stay

For stay, put your hand in front of your dog and make sure that your dog is laying down. move backwards slowly with your hand still sticking out.
Note: Your dog may not listen as well as lay and sit. Be vigilant!