Eat right. Contrary to what some people tell you, you should eat healthy foods, as well as healthy amounts of food. Veggies, fruits, whole grains, healthy fats, and proteins should make up the basics of your diet. Sugars, starches, empty carbohydrates, and unhealthy fats should be avoided as much as possible.
Be sure to drink a lot of water. Avoid sodas (even diet sodas) and minimize your alcohol intake.