Avoid fad diets. It's never a good idea to trade meals for shakes or to give up a food group in the hope that you'll lose weight — we all need a variety of foods to get the nutrients we need to stay healthy. Avoid diet pills (even the over-the-counter or herbal variety). They can be dangerous to your health; besides, there's no evidence that they help keep weight off over the long term.
What's more trustworthy than a diet built by experts from the Mayo Clinic? Created by doctors, nutritionists, and all-star chefs, the plan has a few phases: In the first, you should lose 6 to 10 pounds in two weeks. After that, you can expect to lose 1 to 2 pounds a week until you reach your goal weight. You're also given plenty of resources and advice to help you keep the weight off.