I just posted one of my most recent goals, to get sexy. This post is going to show some of my ideas and math behind my actions. There will be a post somewhere near the end of the week detailing my progress thus far.
The only thing that a person needs to lose weight is a caloric deficit. The bigger your deficit, the faster you'll lose weight. Generally people have no idea how many Calories they are/should be eating. They only have the ball park estimate from the “based on a 2000 Calorie diet,” which doesn't mean anything.
Age, sex, and current weight will all affect your Basal Metabolic Rate (How many Calories you burn each day by just existing, BMR for short). Your level of activity, in addition to your BMR, will determine how many Calories you used each day to maintain you current weight. You can use the Harris-Benedict equation to calculate your maintenance calories. The equation below is the one that I'm using at the time of writing.
= (88.362 + (13.397 x weight in kg) + (4.799 x height in cm) - (5.677 x age in years)) x level of activity = (88.362 + (13.397 x 210.5) + (4.799 x 71 x 2.54) - (5.677 x 24)) x 1.2 = 2516.07
Now you can determine your desired caloric deficit. The rule of thumb is that a pound of fat lost or gained is 3,500 Calories, so to lose a pound a week you should shoot for a 500 Calorie per day deficit. I'm impatient and ambitious, so I am trying to hover slightly lower than 1,500 Calories. This should put me on the track to losing 2 lbs a week, and allow me to overshoot my goal a bit.