Yeah, what Dirk said.
Hit the local farmer's market, if you have one. Don't be afraid to ask questions, though I find myself getting a lot from the local Amish, as their's seem to taste the best, by far.
Quite a while ago, I simply cut out all fried foods - that made a huge difference. I also cut down big time on milk products...that also made a huge difference (after all, we are one of the few ******* that drinks milk as adults - let alone drinks the milk of other *******. Not quite natural, that is).
Read the ingredients of everything store-bought. And even then, keep track of what you get and where, what tastes best and what is making you feel best.
As whimsy said, it seems that the stuff grown naturally tastes one hell of a lot better. It is so easy to tell the difference between a locally and organically grown strawberry and a store-bought.