One way is to avoid eating foods that are very acidic, like oranges, orange juice, tomatoes, lemons, limes, and other citrus fruits,since a high level of acid tells the brain to slow digestion down, which will result in food not being digested as fast, and there for, making you not want to eat.
Second, don't eat too much protein, since this releases certain hormones that also tell your brain to slow digestion down.(Don't take to literally, you still need 1g/lb)
Third, don't eat a lot of foods that contain a lot of sodium, again, sodium also tells the body to slow digestion down, and, again, taking away your appetite.
Lastly, avoid a lot of fiber, since fiber stretches the intestines, bloats you, and makes you think your a lot fuller than you actually are.
Again don't take it completely literal, as you still need to eat all those just not in big amounts.