Here is a "self-hypnosis" tip I use with my clients.
My tip is to go into a state of relaxation. (With eyes closed...Take 5 deep slow "belly" breaths and exhale slowly) Close the fist of one of your hands then open up your eyes and stare at the closed fist. Turn the fist around and around as you continue to look at it. Tell yourself this is the size of my stomach and I am satisfied with a small amount of food. I only eat this size of food. I pay attention to the feeling of being comfortably full and stop. I allow myself to feel the feeling of being comfortably full with a small amount of food and pay attention and stop eating.