Here's a simple diet which is easy to follow, with very few simple rules. This diet is meant for people with a busy weekday schedule.

[edit] Steps

Weekdays
1. Food:
  1. For breakfast, eat cereal or oatmeal with low-fat milk (about 200-250 calories). Your choice - keep it simple and eat the same thing everyday or try a variety of cereals.
  2. The focus of this diet is the weekday lunch. On the day before you start this diet, visit your grocery store and buy plenty of fruits, veggies and greens. If your mornings are busy, you may prepare your lunch while you are eating your breakfast. Your lunch is to consist of fresh fruits, vegetables and perhaps some beans or sprouts. If you need a drink other than water, go for a vegetable juice like V8. Make sure you take plenty of food. Here are examples of what you can choose for lunch:
    1. 5 baby carrots, 2 sticks of celery, 5 spinach leaves, 1 apple, handful of grapes, 1 cup of beans (canned, any kind), iced tea & lemon(no sugar)
    2. 1 orange, 1/2 cup of bean sprouts, a small box of raisins, 5 carrots, 5 strawberries, 1/2 lemon, a V8
  3. for dinner, eat what you normally do. Drink plenty of water. (Optional: start with a salad, a fruit bowl or light soup)
2. Exercise: weekdays, as soon as you get home, use the treadmill or elliptical for at least 15 minutes. If at all possible, go directly to the gym from work.
Weekends
1. Food: eat what you normally do (tip: try out new recipes, try baking bread, go to a fancy restaurant)
2. Exercise: if you normally do (tip: try some new activity every weekend; ever tried meditation? some new genre of music? roller-blading, anyone?)

[edit] Tips

While at work (even otherwise, drink plenty of water)
Its possible and recommended that you eat a variety of foods while following this diet
Cut down on coffee, try it without sugar
Do not snack at work
Buy a clear container for your lunch (glass, if possible). Get your name on it if you are using the office refrigerator to store it.
Make your lunch as colorful as possible.
Do whatever is necessary to ensure you eat the lunch you prepared (for example, leave your credit card behind)
You will notice that you don't feel lethargic or sleepy after lunch. Don't panic, this is normal. You will also become more productive at work; this is also normal.
Assuming you are a busy individual, eating a healthy breakfast should be a breeze. Preparing a healthy lunch while eating your breakfast shouldn't be hard either. The rest is easy (1) eat your lunch (2) No snacks or soda (3) stay busy & focused at work
You will enjoy dinner like never before
IMPORTANT: Don't overdo it by cutting back on other meals. Enjoy life. Indulge at supper-time and weekends like you normally would.