Speak slowly with breaks, giving them room to speak
With a nonverbal child, you become accustomed to not receiving a response and will sometimes desire to fill the silence with more words; however, researchers urge that you not give in to this. Leaving space for your child to respond will encourage them to, and offer them time to create and articulate a response, even if it is only one word.
If you ask a question or see that they want something, pause while looking at them expectantly to show it is their turn to speak. If they do make a sound or body movement, take it as a response and interact with them immediately, showing them that you understand what they have said, giving them power.