General tips
Buy Local Food : Take a child shopping with you, pick up one of the offending products and say quite loudly "Well we’re not buying that, think of the energy it’s used up just getting here!"
Buy Seasonal Food : Food in season is the best you can buy. Apples taste better when they haven't been flown half way around the world. And buying in season encourages local producers who, boosted by factors like the rise in farmers' markets, are building a more sustainable food industry.