Actually good health has more to do with right food (nutrition) than exercise. Sure, lack of exercise does cause its own problems but they can be solved easily the minute one starts exercising. On the other hand, bad food habits are going to screw one's body bigtime with various diseases, including dreaded autoimmune diseases, and usually there's nothing one can do about it other than suffer the effects silently.

In my opinion the biggest change one can make to one's diet is staying away from the consumption of hydrogenated and partially hydrogenated oils. Those things are loaded with trans fats and consumption of them is basically inviting heart problems in the near future. The other big change one can make is avoiding white sugar as much as one can. Just flat out refuse to consume anything that requires white sugar added to it and instead try having them without sugar (in case of drinks) or any other sweeteners.

And now, coming to what one should eat/drink more, I'd say soups. Soups are one of the healthiest foods out there and packed with so many essential as well as rare nutrients if a variety of vegetables and good-quality condiments (naturally fermented vinegar, soy sauce etc) are used. Soups are the perfect food if one is on diet. You just can't overeat it, that's the best thing about it. I feel people in India underrate soups a lot. It should be a part of our daily diet.