My answer is similar to Pilster's (see above). I signed up for a 12-week training program that prepared me for a 5K run. Mind you, I had NEVER been a runner before. But it was a cool class, through my local running/walking store (Fleet Feet), and it was meant for beginners. We started out mostly walking, with short running intervals. Gradually, we ran more and walked less. The best part was meeting all the other women in the class. It was really motivating to go every time.
I also started eating reasonable meals. It seems like such common sense, but it's so easy to forget! For example, if I was really hungry and had NO food with me, I would go to Taco Bell. But instead of getting a meal (like the old me would), I would just order a chicken soft taco. It did not fill me up, but it definitely made me "not hungry" anymore. Then I'd eat a normal meal when I got home.
Last thing -- have you tried the Fiber One bars? Man, they taste good! And they have lots of fiber (obviously) so they are filling. In a pinch, I would eat one of these instead of breakfast.