Hunger Scales

If you've gotten out of touch with your own hunger cues, a great tool to use is a Hunger Scale. There are lots out there - just google it and find one you like. Here's one I found at a blog called Intuitive Eating:

HUNGER - SATISFACTION SCALE (HSS)
10: Stuffed to the point of feeling sick (Thanksgiving full!)
9: Very uncomfortable, tired
8: Uncomfortably full
7: Feel you have eaten just a little bit too much
6: Comfortable, satisfied [stop eating]
5: Just noticing the first signs of hunger [slow down, if eating]
4: Hungry, ready to eat [Eat at this point]
3: Very hungry
2: Extremely hungry, irritable
1: Starving, can't concentrate, dizzy

Try using this scale for a meal or two and see how you like it. Once you get used to eating this way, you will automatically be eating in tune with your own body's hunger and will be getting the right amount of food for you.