When you're really hungry, instead of eating a LOT, try eating food with a LOT of Flavor, i.e. pretzels and salsa, or crackers with garlic lovers hummus. The stronger / spicier flavors make you feel like you've satisfied your hunger without eating so much.
Set a goal of eating more fruits & vegetables, whole grains, etc. By filling up on more of these foods, you may hardly notice that you no longer crave sweets/junk food. Do not force yourself to give up certain foods...you will only crave them more.