To burn the most at every workout you must prepare your body with good nutrients. Carbohydrates are preferred by the body as the main source of energy. There are two types of carbs, simple and complex.
Simple (bad): this type of carbohydrate has the tendency to increase your energy level for a short period of time and is usually high in empty calories (contains high amounts of sugar and little to no nutrients).
If your goal is to lose weight, you want to avoid this type of carbohydrate. A few examples are table sugar, brown sugar, high fructose corn syrup, honey, fruit juice, candy, sodas, and most packaged cereals.
Complex (good): this type comes mainly from plants and fruits, and contains both starch and fiber. Examples: potatoes, dried beans, spinach, apples, oatmeal, pears, brown rice, celery, multi-grain bread, carrots, lentils, broccoli, and tomatoes.
The energy from complex carbohydrates provides more of a slow, steady burn, and it will provide fuel for a longer period.
When I am reading nutrition labels I also look for carbs that are high in fiber and low in fat and sugar. Fiber will keep me full longer and when it comes to weight loss this is important.