I have tried so many times, some have worked and some not so well. I really think you have to have your head in the game and be determined. I always know if I can get to day 4 it will be OK and then not to deviate, with me it starts with Coke, then a chicken salad and before you know it I am troffing a MacDonalds. Stick with the plan and it will work. For the first few days I always do the following:
Try to cut back on carbs the week before
Start on a work day so I am kept busy
Walk the dogs.... alot
Long baths in the evening to stop thinking about food
Lots of water