My own food rules are pretty similar to what Marion Nestle writes, which are never to eat a food with:
More than five ingredients (too processed)
An ingredient you can’t pronounce (ditto)
Anything artificial (ditto)
A health claim on the front (these are always about marketing, not health)
A cartoon on the package (it’s being marketed to kids)
I'm loving this chart instructing you how to eat. It's not that complicated!