I am not sure how to handle it once it is established. My
kids don't give me a hard time with food, there are very few things
that they will actually eat. But we worked with them and got
them into a variety of foods since they were little.
Some of my daughters' friends were a little bit more picky and I
used to ask them what they liked if we invited them to stay for
dinner. If they asked to stay for dinner I would let them
know what I was cooking. Often times I can add a couple
spices such as garlic and I would get them to try it. There
have been times they went back home and their parents asked me how
I got them to eat something they refused to eat at home!