Eat lots of fresh fruits and vegetables, eat lean meats like chicken and fish (especially those high in omega 3's like salmon and mackerel), cook and prepare meals with olive oil in it, enjoy lots of whole
with natural fiber in it. Drink plenty of fresh clean water every day. Avoid refined sugars, saturated fats, smoking, alcohol and drugs (obviously). Get plenty of rest and sleep as well as you can. Manage stress effectively, don't get worked up over every little thing.