Though calorie control is a must, hormonal control is nearly as important. Coupled with calories, hormones govern fat burning. Suppress fat-storing hormones and you can expect a significant amount of body fat to melt away. The ideal way to control these hormones is to keep your carbohydrate intake in check, since carbs kick up insulin, a hormone that inhibits fat breakdown and drives fat storage. Eat fewer carbs and insulin levels tend to moderate, leading to fat loss.
Of course, not all carbohydrates are equal. In short, fast-digesting carbs tend to create a large insulin burst, leading to more potential fat gain. These carbs include white bread, any sweets, rice cakes, white rice, and white potatoes (some body types work well with white rice and white rice if taken at the right amount and the right time).
Conversely, slow-digesting carbs (found in whole-grain breads, oatmeal, sweet potatoes and legumes) don't cause much of an insulin rise, so these should make up the vast majority of your carb consumption.
Do This: The common sense approach is to halve your carbohydrate portions. If you tend to eat a large bagel for breakfast, eat only half and save the rest for tomorrow, or simply eat a smaller bagel. If you typically eat 2 cups of pasta at dinner, eat just one. In time, you'll see the effects of insulin control.
As for carb choices, the aforementioned bagel should be 100% whole wheat, not white. At all times during the day, in fact, choose whole-grain foods over refined ones, the only exception being immediately after a workout, when fast-digesting carbs reign supreme for boosting insulin and replenishing muscle glycogen stores. Keep carbs to less than 2 grams per pound of bodyweight per day.
Note: This is for the average person trying to lose 10-30 pounds, when it comes to competitors trying to get down to super low Body-Fat, it's a little more specific!