This is a question I get asked all the time. There are a few things that you can do to ensure your child eats healthy.
Start early. After 12 months of age, your child can eat pretty much anything you do. Introduce leafy greens and the more bitter greens so they acquire a taste for them. It's ok if they don't like them right away.
Keep healthy fruits and vegetables in the house. If they are not there, they cannot be eaten.
Eat fruits and vegetables yourself. Your children will mimic what you do, if you are giving them vegetables, but eating chips. Your children will want the chips.
Don't give up! It takes at least thirteen times of an introduction to a new food for them to decide if they like it.
Offer the healthy foods often, it should be their main source and try your best to stay away from concentrated sweets. If you do offer your little one a sweet treat, make sure it is AFTER they have had their healthy meal.
When your child is old enough, encourage them to help you cook.. I had my children at the counter helping (or watching) as soon as they were old enough to stand. Another approach is to ask your child to pick out one new vegetable at the supermarket and find a new recipe to make for that vegetable.
Let your child explore the new foods and have fun! This is one of the best ways to encourage healthy eating. As long as you are giving your child all healthy foods, they can eat as much of it as they like.
Grow a garden! This is so much fun to do with little ones. They are more inclined to eat vegetables after taking car of them and watching them grow. I started planting a garden because I wanted my little ones to see where their food came from. We still have one!
Don't let the dinner tabel become a battle ground! Keep the atmosphere light and playful with your child.
If your child decides to test you, and they will, have a plan and stick to it. For example: I have a rule, that I am only making one meal. If my children do not like this meal, they don't have to eat it, but they are not getting anything else. I have never had to follow through. They may refuse the meal, take the meal that you have made and put it in the refrigerator for the next time your little one is hungry. This is their meal until it is eaten. I promise they won't starve; they will get the point that their meals are important.
By keeping healthy foods in the house for your child (and yourself) to choose, you will have less of a battle at the dinner table because the child only knows what you supply.