In addition to drinking a glass of water before a meal think about how your body works. Try these tips to help you conquer your diet.
Fiber - The recommended daily amount of fiber is around 25 grams. Most Americans get less than 50% of that. Fiber will not only keep you full longer (takes a long time to process), but will help your digestive system tremendously.
Time - Slow down when you eat. Your hypothalamus will register your food intake and starts sending signals of satiety at roughly 20 minutes. Before that 20 minutes is up you are likely to just keep eating.
Sugars - The reason that sugar is "so bad" is not the sheer amount of calories. If not accompanied with any fat or protein sugar breaks down and is absorbed very fast. This will result in an insulin spike. Now you have all this available energy and guess what happens if you don't use it? It gets stored as fat! And the worst part: Your insulin levels drop and you feel hungry again. Try to stay away from simple carbohydrates (sugars) and go for the complex carbs. Then couple those with healthy fats or protein (natural no-sugar added peanut butter for example).
3 or 4 days of "dieting" - Don't get me wrong, I am not a fan of any so called "diets", but, if you cut your food intake dramatically for three or four days your stomach will literally shrink somewhat. Keep in mind to not do this for longer, as your body will start using lean mass for energy (which is not something you want).