For a few days, barely eat. Drink milk if you feel hungry. Then only use the smaller plates for your food. Research shows that mentally people want a full plate, and it doesn't matter how big it is, there's this mental block that we have that says something isn't enough unless it's full/covered etc.... Your stomach will shrink a bit over the couple of days that you barely eat, and then you'll start eating more or less normally after that, but 25% less, without even noticing, if you get rid of the big dishes.
I've lost about 30lbs last year without trying.
I wouldn't recommend "barely eat" though. You'll feel tired and miserable. Eat a varied diet... you know... lots of nutrients, but don't eat too much carbs, especially sugar, and white flour. Actually, not too much of any starch or grains.