Eat what a bird eats - raw fruits and veggies (no juices), raw nuts and seeds, and tons and tons of fresh greens (lettuce, spinach, cabbage, kale, etc.). Don't worry about quantities; just eat these things all day long, every time you get hungry. After three days, you'll feel great and they'll be tasting great, too.
Ignore the gimmicks and fad diets. They're just confusing, time consuming, and make you fatter.