Weightwatchers is working for me. I am an online member so it is really convenient. I log everything I eat and I can keep track wherever I am. Exercise is really important, and resisting alcohol (tricky one, that!).
Also, I love chocolate (who doesn't) but I now avoid the milk chocolate junk and have some good quality dark chocolate in the house at all times. Nice cup of coffee and couple of squares really hit the spot without wrecking the diet. I know coffee doesn't help, but there really isn't any point denying yourself completely, otherwise you are doomed to fail.
A healthy lifestyle to maintain your weight is great advice, but if you want to lose, you have to be focused - at least I do! I have managed to 'maintain' my weight for years with a fairly healthy lifestyle. Trouble is, since having children, I am maintaining more weight that I would like!
Good luck!