If this all seems daunting, a good place to start is to just buy fresh vegetables and grains (rice, quinoa, barley, millet) and legumes (lentils, beans) that appeal and if you're not sure how to cook them, find a recipe for them in a cook book or online, and experiment.
The following site has an informative slide show of the important foods to buy organic: http://www.webmd.com/health-ehome-9/slideshow-organic-foods

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[9] What's on my food? Pesticide Action Network North America, 2009, researched June 2009 <http://whatsonmyfood.org/index.jsp>
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