1. Eat lots of fruit and vegetables. They fill you up without adding too many calories.
2. Don't eat out. Restaurants, both fast food and more expensive, are all about getting people to come back. So they prepare foods that are delicious and mildly addicting. Which means they use a lot of fats, greases, and sugars.
3. Don't drink your calories. Be it in the form of juices, smoothies, soda, milk, etc., liquids don't fill you up, but often add unnecessary calories to your diet. Even if they're "healthy" beverages.
4. Drink lots of water. Water increases the efficiency of your body, so you use the calories that you consume more efficiently.
5. Diets don't work. You have to find a system of consumption that you actually enjoy, or your won't stick to it.
We use myfitnesspal.com around here. It helps track what you eat and what is good and what isn't. A couple of others things is I use dashingdish.com and skinnytaste.com for recipes and have found quite a few that are delicious and even my family (with little boys) enjoy.