I agree with the pp - you have to stop seeing what you're doing as a short term thing, aka 'diet', and more of a lifestyle change. Make slow changes that you can live with FOR LIFE. Pick a plan that suits your tastes - a lot of people do a lot of different things to lose weight, and they all work. The secret is to find the one that YOU can stick with. (and no, it doesn't have to be part of an organization or club - there is a plethora of information for free on the internet)
As far as the nightime snacking goes, I really think it's a habit. I used to do it all the time, and it was part of the reason that I slowly slowly crept up in weight over the years. So I just stopped - about 6 months ago now. At first it was tough, and I felt like I was missing something - now I literally don't ever think about it. My habit now is to have a cup of herbal tea in the evening. It makes me feel as comforted as having a snack ever did, and the bonus - no guilt afterwards!
Good luck with your journey, have fun with it, be kind (but firm!) with yourself, and keep on going, no matter what happens. You'll be so glad you started in about 3 months from now!