If you're trying to lose weight, it's important that you know your daily calorie needs. One of the reasons many of us struggle to lose stubborn pounds is that we overestimate how many calories we need each day. On top of that, we also underestimate how many calories we consume throughout the day.
You can use this Daily Caloric Expenditure calculator to determine how many calories you actually need each day. Once you have that number, you need to create a deficit -- either by dieting or exercise -- of approximately 500 calories per day to lose a pound a week.
To make sure you're staying on track, use a food database or calorie calculator to find out how many calories are in the foods and beverages you're consuming. You may want to keep a food journal to write down what you're eating and drinking. Not only will you be able to see, at a glance, how many calories you're taking in, but knowing you have to account for every calorie will also make you think twice before eating when you're not really hungry. Some runners use their training journals to also track their calories.