"Cook."
Cooking your own food is the only sure way to take back control over your diet from the food scientists and food processors. The only way you can really guarantee that you're eating real food, rather than edible food-like substances, with unhealthy oils, high-fructose corn syrup, and loads of sodium, is to prepare it yourself. It isn't surprising that the decline in home cooking closely parallels the rise in obesity.
All the tips given for the 28 Days of Real Food Challenge were compiled from "Food Rules", by Michael Pollan.