Fiber is key. Eat lots of it and you'll stay fuller on fewer calories. Generally, foods with lots of fiber are also healthy foods that fit into a well balanced diet. If you look at the recommended amount of fiber for the average man then look at the amount of fiber in normal cereals, breads, and snacks, you'll see how hard it can be to get that amount. I think I come close to the recommended amount most days but I also eat a high fiber cereal (Oatmeal square, shreaded wheat, or Kashi GoLean) every morning, a sandwich on whole wheat bread (note: most whole wheat/grain breads don't have much fiber. be sure to read the labels. Roman Meal 100% whole wheat bread has 5 grams of fiber per slice or ~20% of daily needs), and dried fruit as a snack during the day.