Like Kerry we do the repeating back thing with our kids. It wasn't intentional, it's just what we naturally do to teach them speach. When my 15 month old says "ca" I say "Yes! Car." when she says "Ba" I say "Yes! Bath, you wan to have a bath". When my older toddler says something I am not quite sure of I will repeat back my best guess at what they said. But other than that I think it's just parenting and discipline to manage their behaviour as they learn to talk. As well as learning to talk they have to learn acceptable behaviour and how to manage frustration. I would read some really good parenting books, I like "easy to love, difficult to discipline" and "raising your spirited child".
Please excuse my typos and lack of caps, I am on my phone.
