I've tried bribing them, threatening 'no dessert', asking them to have 'just one more bite', etc. So I came across this article tonight and loved it and wanted to share it with you . . . unfortunately, it looks like that article is no longer available for some reason.
There were a lot of great ideas in the article but the main thing I took away from it was: you decide what to serve and when, and they decide what to eat and how much. No bribes, threats, or un-happiness at the dinner table.
The article recommended a book from Amazon, there is the book they recommend. Check it out!