PART I: What Should I Eat?
RULE #12 - Shop the peripheries of the supermarket and stay out of the middle.
Most supermarkets are laid out the same way: Processed food products dominate the centre aisles of the store, while the cases of mostly fresh food - produce, meat and fish, dairy - line the walls. If you keep to the edges of the store, you'll be much more likely to wind up with real food in your shopping cart. This strategy is not foolproof, however, since things like high-fructose corn syrup have crept into the dairy case under the cover of flavoured yogurts and the like.
"Eat food. Not too much. Mostly plants."