When trying to lose weight you need to keep in mind that in order to lose one pounds week you must have a 3500 calorie deficit, in other words you need to burn or eat 3500 calories less than you do now to lose that pound. It's recommended that you lose only 1-2 pounds a well for health purposes as well as preventing lose skin.
There are different ways to reach this deficit, either cut you calories you are consuming by 500 a day, or burn 500 calories a day through exercise. Some people cut their intake by 250 calories and burn the other 250 through exercise. I went with cutting it out of my intake, all 500.
The first thing you need to do is find out what your BMR is. BMR is basic metabolic rate or the amount of calories your body needs in order to survive. I have provided a link to a BMR calculator. You then need to find you TDEE TDEE is your total daily energy expenditure or the amount of calories you burn with everyday activities. Eating below your TDEE but above your BMR will result in weight loss.
My TDEE is 2475-20%=1980
My BMR is 1680
Therefore if I eat 1980 calories a day, and exercise 3-5 days a week I will lose a steady 1-2 pounds a week.
For each 10 pounds you lose you need to recalculate your TDEE. However never eat below 1200 calories..that is dangerous.
If you plan to exercise for your deficit each day then I highly recommend investing in a good heart rate monitor, one that tracks your calories burned. If you can't afford to do that then average your heart rate during exercise and use this equation to find your burn. It is very accurate.