Avoid foods that are "lite/low-fat/nonfat"! Because removing the fat from foods doesn't necessarily make them non-fattening. Carbs can also make you fat. Many low/nonfat foods boost the sugars to make up for the loss. While demonizing 'fat', we give a free pass to other, allegedly "good" nutrients.
Since the low-fat campaign began in the late 1970's, Americans actually have been eating more than 500 additional calories per day, most of them from refined carbohydrates; like sugar. The result is the average male is 17# heavier the average female is 19# heavier than in the late 1970's.