I've always been told that eating right and exercising regularly is the best diet out there. This is the diet a friend of mine was on while she was on weight watchers...
Breakfast:
1 slice of whole wheat toast (can have a small amount of butter/jam), 1 small low fat yogurt or some fruit
Lunch:
Turkey sandwich (can have a small amt of mayo or mustard) with some fruit and some juice (make sure it's 100% juice or it's just a sugar filled sports drink)
Dinner:
Boneless, skinless Chicken breast, cooked with some Kosher Salt, black pepper, some garlic, a little all purpose seasoning and Olive oil to keep from drying out (or herbs of your choice)
You can put almost anything you want in place of the suggested food items, just make sure that any meat you buy is trim and low fat ... like ground sirloin instead of ground chuck, it's a leaner meat therefore, it's healthier for you. Try not to buy any beef that is less than 80% lean and 20% fat. You should also buy a kitchen scale to measure out your meat; the average portion size we need of meat is between 4-6 ounces. That doesn't sound like a lot, but it's the truth. In addition to that, make sure that anytime you snack that it's healthy; a piece of fruit, some vegetables, some nuts (if you aren't allergic) and drink plenty of water! It'll help flush the bad stuff out of your system.
In conjunction to this, start taking daily walks. Start at 1/4 of a mile, then work up to a half then up to a whole mile etc. After you've gotten used to walking on a regular basis, change it up; walk 1/4 mile, then run 1/4 mile then walk 1/4 etc. Eventually, you'll lose weight in a healthy way. Remember, you don't want to drop it all at once, that's not a healthy way to do it at all. A good friend of mine lost >150 pounds that way in about two years! Good luck!