What helps me is waiting 20 minutes after eating my dinner. It takes your body about 20 minutes to tell your brain that is it full, so if you go back for seconds too soon you end up over eating when really your body has had enough. I find that drinkin a big glass of water after dinner will help you feel more full.
Another tip that can help is eating your food very slowly, this will give your body time to communicate with your brain and let it know that it is full. Chewing your food slowly/properly also aids in the digestion process.

~S