No Snacks, no sweets, no seconds. Except on Days that start with S. Too simple for you? Simple is why it works. Look here for questions, introductions, support, success stories.
I am just back from a short vacation and although I only had two S days on the vacation I am finding it difficult to get back on track now. And if I hadn't eaten so well on the S days maybe I wouldn't be having so much trouble. It makes you wonder if its all worth while!
The best way I've found is to get back on track is to "eat well on N-days."
Plan special meals that you love for your N-meals. For me, that would be things like shrimp, or fresh strawberries... totally "legal" but yummy and perhaps a bit of a treat.
Good luck.
Once the habits are in place, it gets much easier.