There is a good article in February's copy of Bon Appetit. The article is titled "50 Easy Ways to Eat Green". Among the better tips:
#8 Buy a Side of Beef - from your local farmers' market.
#9 Cook More Often - and avoid many of the preservatives and some of the packaging of processed foods.
#18 Be Your Own Barista - reduce the waste of a paper cup from the coffee shop, buy fair-trade organic coffee, and save a few dollars a day.
#21 Make Your Own Cereal - the magazine version of the article has a good recipe which includes flaxseed, oats, walnuts and brown sugar.
#29 Eat Grass-Fed Beef - cows are meant to eat grass, not corn; cows raised on the open range don't require waste management infrastructure and improve the fertility of the soil.
#35 Become a Locavore - buy from local farmers, reduce the carbon footprint of what you eat and help your local economy.
#45 Pack Your Own Lunch - and reduce the amount of fast/processed food you eat.
and:
#4 Don't Read The Omnivore's Dilemma by Michael Pollan. Instead, they suggest you read Pollan's (. . . you guessed it) In Defense of Food.