A calorie is a calorie and you should try to stay within a certain number (based on your weight, height, etc....there are calculations for this). You need to expend more than you take in. That is the obvious rule. However, on Atkins, you are stressed to focus on carbs instead of fats. USDA has been teaching us to focus on low fat/low cal diets. The recommended grain serving is around 11 or so. To me, and to quite a few people, that is too much unless you compete in triathalons on a regular basis.
Sometime last month, I ate roughly 2,500 calories in one day and I stayed at 9 grams of carbs for the entire day because of what I ate. The next day, the scale dove 3 pounds. I don't eat that much on a regular basis, however, and I try to keep my calories around 1,800 or so. Even less if I do not plan any cardio activity.
If you find yourself reaching for food when you aren't sure if you want it, take a brisk walk around the block, drink a glass of water, or log onto the web for fitness programs (even if you don't partake, reading and looking at photos is enough to keep that cookie out of your mouth).
My biggest helper is brushing my teeth. The desire to eat goes away with a clean mouth.