Does he like balls?
Sit on the floor, opposite him, with a ball. Tell him you will pass the ball to him if he asks for it using his sound. Any sound he makes, he gets passed the ball. Then you ask him for the ball, such as if his name is Max "Max, push ball to mummy". Keep language simple and an instruction.
Repeat this as many times as he will put up with, which at first may not be many, but you may find he likes the game.
Can do the same with toy cars, or anything that you can pass between you which he likes.
When you go up steps, count the steps out-loud.
Reading books to him is great. Do that a lot. Look at pictures, point to something in the picture. Looking at a picture of an Elephant: ask "Max, What is this?"... wait, wait, wait... give him time to respond in some way. "Elephant. That's right Max, Elephant"
When out an about, "Max, look. What is this? (point to the bus)". Max makes any sound. "Bus, that's right Max, bus".
Keep modelling words for him. Make it a game and keep the game short, unless he is indicating he wants the game to continue.