Despite what you may think, losing weight isn't a mysterious process. In fact, weight loss doesn't even have to involve strange diets, special exercises or even the 'magic' of pills or fitness gadgets. Want the secret to weight loss? Make small changes each and every day and you'll slowly (but surely) lose those extra pounds.

Rules of Weight Loss

To lose one pound, you must burn approximately 3500 calories over and above what you already burn doing daily activities. Whew...that sounds impossible doesn't it? Here's how it works.

Calculate your BMR (basal metabolic rate). Your BMR is what your body needs to maintain normal functions like breathing, digestion, etc.
Calculate your activity level. Use a calorie calculator to figure out how many calories you burn while sitting, standing, exercising, lifting weights, etc. throughout the day.
Keep track of how many calories you eat. Use a food journal to add up what you eat and drink during the day. If you're eating less calories than you're burning, you'll lose weight.
Example:

Mary's BMR is 1400 calories and she burns 900 calories in daily activity. To maintain her weight, she should be eating 2300 calories but, after keeping a food journal, Mary finds that she's eating 2550 calories every day. By eating 250 more calories than her body needs, Mary will gain one pound every 2 weeks.
This example shows how easy it is to gain weight without even knowing it. But it's also easy to lose weight. In fact, you can start losing weight right now by making a few simple changes. If you can burn an extra 500 calories each day, you'll lose a pound a week and you won't even have to change your clothes.

source:/exercise.about.com