Ming from Agents of Speech teaches how to help delayed children understand and follow verbal commands. For speaking kids, she uses rehearsal with gestures that fade over time, plus controlling access to objects during practice. For nonverbal children, focus on getting single words first before moving to command comprehension.
Once you know your child doesn't understand commands, what you do is to teach with rehearsal. If your child can speak, then you can use your rehearsal. Say after me, put this on the sofa with a gesture. Go do it right the next time. You reduce your gestures and you also reduce the emphasis on the keyword and see if the child can do it or not. If you're doing contrastive commands, the best thing to do is is to do a rehearsal. Don't allow the child to touch the things on the table or on the floor or wherever yet. And tell them to say it once. Have to say it once and let them do it when you're saying it. Add gestures as well. Nine times out of ten, if your child is already verbal, it's just a matter of time. What if your child is nonverbal? That's not the main thing that you should be working on. If your child is nonverbal, you should think about how to get your child to speak at least the first word, single words, and then we can think about this.
