I am very much AGAINST diets. They are quick fixes and will never last in the long term. You will find all the other professionals on this website share my opinion too - fad diets do not work, period.
The important thing to learn when losing weight is to change your lifestyle habits permanently. At the end of the day, if you go on a diet for a certain amount of time, you will most likely lose weight. But when you come off this diet, that is when you begin to realise that you won't know how to eat for the rest of your life. In the long term, the weight will inevitably creep back on.
Generally speaking, depending upon your body and your lifestyle, you will require X amount of calories per day to maintain your current body weight. During your 'diet', typically you will consume LESS than X calories in order to lose fat. When you lose the desired amount of fat, in a sedentary state you will require LESS calories than before because you are carrying around less body mass. The problem is that many people will revert to their previous eating habits and thus gain all the fat back. Often additional fat is gained from binging as a result of people unhealthily starving themselves of foods during their 'diet'. This is what is commonly known as yo-yo dieting.
So how to combat this problem? Number one is to educate yourself. You should know what a calorie is. You should also know what proteins, carbohydrates and fats are and why each of these nutrients are required by your body. To get you started, I have written a very brief overview at:
So once the fat has been lost, a new caloric intake must be established. You should find foods that you love to eat and integrate them into a healthy lifestyle eating plan. Lean meats, vegetables, fruits, grains, dairy and eggs can all be extremely healthy when all eaten in moderation. But remember - if you struggle to stick to an eating plan in less than 24 hours then find another alternative - you want something you can enjoy for more than 24 years.