Create Positive Food Experiences.
Make eating a positive experience. Reward kids when they try a bite of a food they rejected before. A happy face sticker is a fun incentive for little children. Doing this delivers a positive association with that food.
Young children don't follow logical thinking patterns and arguing with them or punishing them for not eating their vegetables will just create stress for everyone and will result in a negative meal experience. The kids will associate the vegetable with a bad feeling. Such negative experiences could actually increase picky eating.