One way to make sure you don't overeat is by slowing down so that your stomach has time to register that it's full. There are plenty of tricks to keep yourself from scarfing down dinner, such as eating with your non-dominant hand.
Here's an even easier one: Make sure you put down your fork between every bite. If you're eating something with your hands, such as pizza or a sandwich, put down the actual food. Then, don't pick up the fork or food again until you've chewed and swallowed the previous bite. When you start to feel full, put down the fork altogether!
The forced pauses will prevent you from racing through your meal and give you more time to savor it. Plus, not only is this a healthy eating tip, but it's also good table manners, don't you think?