This means sensing your Physical Hunger and Fullness and only eating when you are physically hungry and stopping when you are physically full. Second is not letting Emotional Hunger or Fullness play a role in your eating, I will talk about this more in posts to follow. How many times have you finished your plate just because the food tastes so good? That is not stopping when full - and results in eating too much. Also, have you not eaten when you were physically hungry because you know you want to eat more in a few hours? You are slowing down your metabolism every time you don't eat when you are hungry.
Try to really listen to your body and eat when it tells you to and stop when its finished.