We mastered the art of reverse psychology, tricked the heck out of them, and to this day my kids are the only ones I even know about who eat basically everything....
Here are my hopefully helpful hints..
Start out with lots and lots and lots of praise for choosing something you want them to eat. Makes them really proud, and chances are, they will repeat that behavior.
Never dictate what they put in their mouths. Never make them finish anything they don't like. That is the best and quickest way to get them to turn mealtime into power struggle time and prevent them from ever wanting to try new foods, because they will always be afraid, that if they don't like it, you will still force them to eat it (think about it, grownups would hate that too... think about someone forcing you to chew on a chicken leg.... YUCK). Be silly. When you set the table, and would like them to have a vegetable, tell them, they can't have it. Make the vegetable cry big sad veggie tears for not being allowed in a cute little kids mouth, take the veggie from your kids plates, and pretent to eat it, have the veggie plead to be put in a kids mouth and not in a stinky grown up mouth with huge teeth.... I tell ya, so far, it has worked on all kids I know, even the ones who don't eat anything at home. As soon as kids come to my house, we explain the house rules to them "You never have to eat or try anything you don't like, and you never have to finish your plate". Once kids understand that concept, they will even try new foods, just to please me, and get a round of applause from all my family members for being courageous enough to try. Make it fun, make it silly, and I promise that the only foods your kids will not eat are actually the ones they really find distasteful ( for us it is mushrooms for one kids, and peas for the other).