I don't have any real "methods" for you, but I was the same way and I CAN tell you that it DOES get easier. After a month or so of eating healthier foods, your cravings for heavy, greasy, fat-laden foods definitely subside. For example, I used to eat cookies everyday with my lunch (and of course I thought I just HAD to have them), but after I simply stopped packing them, I realized weeks later that I didn't even miss them. You learn to choose quality over quantity - treating yourself to a small, but really good bowl of chocolate ice cream after a week of healthy eating and exercising will appeal to you more than having a donut every day for breakfast.
Also, when you cut back on your portion sizes, your body readjusts and learn what feels "full." And you should never feel stuffed, just satisfied. Trust me, a large helping of nachos and cheese feels like a rock in your stomach compared to a yummy salad with lowfat cheese on top!!
I know it's hard right now, but if you hang in there it will be worth it, I promise