The number one requirement for a healthy smile is good and regular brushing and flossing, but you knew that.
I used to work in a dental school library, and I came across some interesting research. The germs that cause tooth decay thrive in an acidic environment. Therefore the order in which you eat foods has an effect on the pH factor in your mouth.
Eating sweets or drinking fruit juices makes your mouth more acidic. Even rinsing with water won't help much, because water in neutral. Drinking milk, or eating cheese (cheddar at least) or peanuts changes your oral chemistry from acidic to basic, and the germs don't like that. So follow up your sweets with something like that.
I had actually seen something about that in one of my books before I started working there. So of course, I looked up the citation. I still have the book and can still probably find the citation. Of course, I left that job in 1983 and have no idea what the current state of research is. My guess is that more foods have been added to the list of those that protect your teeth from sweets.