I don't care too much about organic foods. They're too expensive for the value. I have a simple strategy though.
I look at the health facts and check a few things.
First, I compare the daily percentage of Total Fat to the percentage of Saturated Fat. Heavier on the saturated=unhealthy.
Next I look at sugar. I compare the percentage breakdown of Total Carbs, simple sugars, and Fiber. Healthy food will have a greater ratio of Fiber than empty carbs, and not many simple sugars.
I then compare the percentage of daily "bad stuff" (total fat, sodium, sugar) to the number of Calories. If I assume I'm eating a 2000 kcal diet, I want the percentage of bad stuff to be less than the percentage of my daily intake the item should be.
Same goes for "good stuff", vitamins and such. The daily percentage of vitamins should be greater than that same ratio of calories in the item to daily calories.
I also try to cut down on high fructose corn syrup, refined sugars, processed foods, and preservatives.
Items that pass the first two tests then to pass the later two. It was interesting when I compared some frozen meals I ate at work to the "diet" frozen meal a coworker was eating. Her "Healthy Choice" meal had fewer calories than my "Marie Calendar's" one, but they had equal fat content, mine had less saturated fat, and mine had more fiber. I would also be less hungry later.
In general I like to eat whole grains, dark veggies (loves me the spinach), and lean proteins (fish and eggs, yum).