Tell them they like them

I started my kids on fruits and veggies from the time they started eating whole foods, always offering a colorful selection.
Whenever we sit down to eat and my children ask me if they like a particular fruit or vegetalbe, I always tell them you loved it the last time we had whatever it is, even if I had never served it before and then they eat it and usually like it.
I also keep bananas on the counter in plain view for snacking and washed grapes on the lower shelf at eye level for my young children so that when they open the fridge they see a healthy snack before anything else.