You need to be disciplined - its a
habit. Just like you can get into the
habit of
eating to wrong food, you can get into the
habit of eating the right food.
Exercise - the more you do the better. If you can do an intense 1hr / day, with the right diet, you will see results very quickly.
Basically, you need to burn off more calories, than you take in - then you'll lose weight. If you get your diet right, it'll stay off for good.