There are some wonderful tips from Michael Pollan's In Defense of Food. But, lets start with the thesis.
His main prescription, which manifests itself in his mantra (eat food, not too much, mostly plants) is quite simple, yet (in American terms) close to impossible for the vast majority of busy Americans. It is this:
1. Escape the Western Diet* (he believes all traditional diets are wonderful, apart from ours which is heavily processed, full of sugar, destructive to the planet and individuals- tooth decay, diabetes, cancer, etc.)
2. Escape the Ideology of Nutritionism (this cannot be done justice apart from his book. However, it is an ideology- not science-that separates a diet from its culture, individual foods from their diet and the chemicals, minerals, vitamins, etc in a food from the actual food. It has led to additives in processed foods, never ending studies trying to figure out what part of food is good and which is bad- separate from the food itself)
*diet in the traditional sense- a way of eating. it has nothing to do with most people's definition of diet- eating less.