I set a date, for me it wa January 1 2005, then started changing my lifestyle. I started eating breakfast, cut out snacks, and avoided take out meals. My basic eating was already healthy, but it was the rubbish I ate between meals and my occasional (like three times a week

) takeout habit that was causing the problem.
Then once I had the eating controlled somewhat, I added exercise. My exercise regime has really grown since I have lost weight. I started by walking, then swimming, then doing gym, now I do all sorts of stuff.
You have to make weight loss and healthy living the first priority in your life, for it to work. You have to plan, be prepared to make sacrifices, but also still have fun.
If you have unresolved issues in your life, you sometimes need to take hold of those as well. For me, I am a stress eater, always have been. Now I do yoga and pilates to help manage my stress, and I do cardio when I am in acute stages of stress instead of eating.
It's a long hard road if you have a lot of weight to loose, and it's not easy, but perhaps with commitment, it's not as hard as you think it will be.