When asking questions, avoid questions with yes/no answers. Instead of asking, Do you want something to drink?, ask Do you want milk or juice? If they cannot answer, get the milk and juice out, let them point, then say the word for them. Use this technique with getting dressed, blue shirt or red shirt and any other time you can give them a choice.
Sing songs while doing the hand movements. Some good ones to start with are Head and shoulders, knees, and toes and the Itsy, Bitsy, Spider. Also, nursery rhymes or other traditional songs are good to practice.
Read books. Read simple books with great pictures and one sentence on the page. After you have read the book several times, pause/leave off a word at the end of the sentence and let the child fill it in. This is also good to do with nursery rhymes. After the child knows it, pause and leave out a word and let him fill it in.