On the most basic level, any weight loss or healthy living plan will only be effective if it enables you to burn more calories than you take in each day. You can choose any successful diet plan out there -- it doesn't matter what gimmick is used to accomplish the weight loss, the reason for the weight loss is directly correlated to caloric intake.
How many calories each person needs each day is going to vary depending on a variety of factors including age, weight, height, activity level, etc. Luckily there are many online calculators out there that can estimate the amount of calories you need each day to accomplish your goal -- whether that goal is losing weight, or simply maintaining your current weight.
Basal Metabolic Rate (BMR) Calculator: BMR Calc
The BMR calculator will give you an estimate of the amount of energy your body would expend if you basically just laid in bed all day. The online caloric intake calculators will use this BMR figure, along with your standard activity level, to determine approximately how many calories you need to consume to accomplish your goal. The following calculator will provide three different intake options: one for maintenance, one for fat loss, and one for 'extreme' fat loss.
Daily Caloric Intake Calculator
I have used both the standard "fat loss" and "extreme fat loss" figures in the past to determine my daily caloric "budget", and have found both to be effective. I currently use the standard calculation because I am in this for the long haul, and found the extreme option to be overly restrictive, and it was too tempting to binge after several days of limiting myself to 1500-1600 calories (especially when accompanied by regular exercise).
For maximum effectiveness, I suggest using a smartphone or iPod app that will track your calories for you -- some of them even have extensive food databases. I have had good luck with the free version of DailyBurn Tracker, and found the barcode scanner to be useful for many pre-packaged items that I consumed. A quick Google search for "Calorie Counter App" will tell you that there are many other options out there, too.
The idea of tracking every calorie you ingest may seem like a real bother, but it really helps you grasp the amount of calories in the different foods you eat, and eventually you may not even need to use the tracker. My daily eating schedule is routine enough that I no longer need to track with an app -- I know that I will have approx. 1000 calories available for dinner and dessert, so I will try to make appropriate choices when I fill up my plate. But if I hadn't spent time tracking every calorie, I wouldn't know that a piece of whole grain bread is going to have ~110 calories, or that a typical piece of pepperoni pizza is going to have ~300-350 calories.
No, this calorie counting thing isn't very glamorous or exciting, but it is effective, and it is part of the Glutton Free way.