First, it's important to state right at the beginning that this advice only applies to parents of infants who haven't begun eating solid foods yet.
The struggle of dealing with picky eaters is real. The funny thing is that the picky eater in my life isn't my child - it's my dad. He has a long list of foods he won't eat. Although he is 90 years old now, sometimes it feels like he is a toddler, so I can relate to parents who struggle with children who are picky eaters.
Growing up, I didn't notice how much of a picky eater he was, but now that I live with him again as a caregiver, I'm constantly disappointed to see how often he rejects eating some of the things I make. He has all kinds of wacky rules like he'll eat raw cauliflower but not if it is cooked. Or, he'll eat cooked spinach, but not if it is raw, like in a salad. He won't eat many vegetables I like to use in cooking, such as asparagus, broccoli, or even onions. He grew up during the Depression in rural upstate New York. According to him, his mother was a lousy cook. The scenario I imagine when considering how closed off he is to new tastes is that he grew up in a time with limited food access and a parent who didn't cook well.
What makes dealing with my dad as a picky eater stand out even more is that his grandchildren are the polar opposite. They'll eat anything. How did we go from picky to adventurous eaters in three generations? Although epigenetics may play a role, I attribute the fact that my adult daughters will eat pretty much anything to how effective the strategies below were in shaping their taste and relationship with food.
Keep It bland and Carry On
If you keep things bland from the start, your palette only knows bland. It doesn't know about the joys of sweet, spicy, or savory. The moment your palette gets exposed to something other than bland, it sets an expectation that everything you put in your mouth will have flavor. Think about the logic that applies to learning to drive. If you start with a manual transmission, then it is easy to switch to automatic, but the opposite is necessarily true. For food, if you start with bland, it is easy to switch to savory, sweet, or spicy later on, but it is impossible to go back to bland after getting a taste for savory, sweet, or spicy. The recommendation here is to avoid using any elements that add flavor to food if you're making it from scratch.
Skip the Salt!
This strategy is an extension of the first one. If you have yet to notice, processed foods have a lot of salt. That's what makes them so tasty. Salt makes everything better. The problem is that once you have it, you expect everything to have it. 
Imagine your toddler who has eaten nothing but unsalted steamed broccoli tastes a piece of broccoli that has been salted. Good luck getting them to eat unsalted broccoli again. The recommendation here is to avoid processed foods, which are full of salt, and avoid salt in your home-cooked meals.
There's a Reason a Teaspoon of Sugar makes the Medicine go Down
I come from a long line of sweet tooths. I hate how I crave something sweet at the end of lunch and dinner. Still, I'm not surprised knowing how sugar releases the neurochemical dopamine responsible for feelings of pleasure and satisfaction. Like many people, I'm sure I've been conditioned. It started when I was young. My parents didn't think twice about feeding me sweet chocolate cake on my first birthday. 
With this in mind, I am still amazed at how effective the strategy of avoiding sugary things has made my daughters utterly disinterested in eating desserts. The recommendation here is to hold off on giving your child sweet things for as long as possible. This is easier said than done. It is easier to do for your first child than for the second child. We didn't give our first daughter any dessert until she was between 3 and 4. It was harder to hold off that long for our younger daughter because she was at my older daughter's birthday celebrations.
Introduce as many Vegetables as Early as Possible
The Japanese say that you should strive to eat at least 33 things each day. One way they achieve this is by eating a wide variety of vegetables at all three meals in small amounts as side dishes called okazu. 
Many of these side dishes are different preparations of vegetables. Vegetables are great for many reasons, including the fact that they are a good source of fiber, contain many nutrients, have alkalizing properties, and the fiber helps you feel full. The Japanese get so many vegetables by having different preparations of vegetables at each meal using an impressive range of vegetables from kelp and seaweed to burdock root, baby bamboo, spinach, pumpkin, and mushrooms. The range of flavors and preparations is vital to their strategy to stay healthy. It also functions well to keep children curious about eating.
Say Hello to the Stinky and Gamey Foods
The final strategy is to introduce stinky and gamey foods early on. When my daughters switched to solid foods, their Japanese mom would boil short-grain rice with baby whitebait fish to make a kind of porridge. 
The whole house stunk of fish. It was as stinky of a meal as you can imagine, and it tasted like an ocean water milkshake. Fast forward to today, and both of my daughters will eat all manner of things that come from the ocean. The same logic should apply to gamey foods like lamb. I didn't grow up eating it, so I never developed a taste for it, but I'll bet if I had been fed gamey foods, I would enjoy eating them more.
