I don't go in for all these faddy diets, but I do try and stick to low fat foods. Plenty of chicken, salads, low fat dressings, fruit, nuts, yogurt and at least 2 litres of water a day.
If you feel hungry during the day don't snack! Drink a large glass of water, it will surpress the munchies.
I do, or did before I broke my leg, go to the gym 3 times a week and swim for an hour in the morning 5 days a week.
I like to have a blow out now and again, with the exercise I never have to worry about the chocolate muffins, beer or take outs. But I do try and limit them to the weekend.
Oh, and plenty of sex. That way you can have your cake and eat it.
It's not for everyone, but works for me.