I also do the your not leaving until you have one bite, which normally after the one bite they try to act like they hate it but don't wanna show it so I follow with oh just one more bite and then another, then its all gone. I also don't cave into much on when they want a snack or what have you cause its you get what you get I hate spending money and wasting the food. So I think this helps that they know I am not gonna buy them anything else so if they are hungry they will eat it.
I remember when Brian started liking a hamburger at mcdonalds which is way cheaper then chicken nuggets! That was a great day and a huge help to my wallet when I wanted to take them out for a quick meal. I don't know but I would say a big factor is just have your kid try everything and anything cause you might fine they like a lot more then even you would ever think to give them, which can save you money.