Growing up my family always ate pretty healthy. It's kind of second nature to me, but I've had to teach others how to eat healthier. Not even healthier as much as "more flavorful" lol.
The biggest thing that people respond to is when they eat something I've seasoned with fresh citrus. There is absolutely no substitute for fresh citrus zest and juice! Best thing ever! Try it. Also, I mostly cook with coconut oil (when I have to--I definitely don't deep fry anything) because it adds an ever-so-slight sweet/clean flavor to everything. And despite being full of saturated fatty acids, it's still somehow good for you. I use olive oil for pastas and Italian dishes because it adds that unmistakable "Mediterranean" touch.
Oh, and if you're someone who has a sweet tooth (like my current guy) try using splenda instead of sugar. It's more expensive obviously, but it's worth it.
If you have a spice garden, grow garlic. Not to use the bulbs themselves, but for the greens. They have a very unique flavor. Somewhat like garlic and green onions combined, but it also adds it's own special flavor. (Difficult to describe with words, but if you ever try it you'll know what I mean.)
I'll post more ideas as I think of them. I actually have quite a few. I'm known as "the cook." XD