Eat real food, get enough sleep, do some strength training, walk lots.
Diet - I used to think it was all about low carb, or high fat, or paleo....now I am not so sure. I avoid wheat because it makes my stomach unhappy, but otherwise I eat all sorts.
Exercise - some basic, safe strength training goes a long long way to promoting all sorts of health. However, there are so many fads and crazes out there. So much too which is written as if we are all elite athletes or physiotherapy patients.