Floss. Poor dental health affects overall health significantly.
Eat well. Sugar is hidden in everything and home cooked food from basic ingredients seems to be going out of style.
Keep active.
Get healthy sleep.
Meet other humans and do stuff with them.
People will do lots of other things and have small "health hacks". But if you don't get the basic things right then it's not really something you can fix by taking "antioxidants" or other measures.