I know this is unsolicited advice, so feel free to ignore me if you want.
That said, I agree with Krystal about the South Beach diet. I've been doing it since Aug 31st, and I've lost over 16 lbs!! I must be honest that I'm pretty sedentary too. The first two weeks are pretty rough in my opinion. We ate a LOT of salads those two weeks, but you probably would want to go with soups as its cold now. Have lots of low-fat, high protein snacks too. Once those first two weeks are up it gets a lot easier.
As for keeping on track with any diet, I'd highly recommend buying a cheap pock