I completely agree with Tiffany - PROTEIN is the key to my success. I eat low salt ham, low fat cheese, lean chicken etc as a snack and it really works to keep me full for longer. In fact I saw a programme on the BBC called something like the science of food in which they did experiments and proved that high protein meals keep you fuller for longer than every other type of meal.
I also think soup is a great help - I tried this after watching the same Science of Food programme. They explained that your stomach is like a sieve, if you drink water and eat solid food the water can filter through the food and out of your stomach quickly so you stop feeling full. However, if you eat soup the food / water mix sits in your stomach and drips out slowly (in the same way it would if you put thick soup into a sieve) and this means you stay fuller for longer.