Here is a really useful modeling technique that we often use. It is called simultaneous modeling. It goes something like this.
**I first demonstrate what I want the child to do:
"I want us to try and say the word /car/"
"I will say it first then I want you to say it with me, ok?"
Teacher: "Car" (very slowly, maybe a few times)
Teacher: "OK now let's try it together"
Teacher and Child: "Car...Car..Car" several times slowly.
**Depending on if you are seeing any success you may wish to speed it up or slow it down. When I begin to see some success often I will say the word three or four times more; when the child thinks I am going to say it again I will drop out and they will often say the word on their own.
This has been a useful and easy technique that I have used for years.
If success does not happen right away try it again at a later time. Always give positive reinforcement to the child for trying;-)