The most important nutritional advice I can offer is to change your mindset around eating and food. In my experience, the people who have managed their weight most successfully are those who have changed their mindset around food.
It is not unusual for many of us to associate food with reward (pleasure) or relief from pain. If this is the case, no matter how much willpower you attempt to exercise you will ultimately fall victim to your conditioned need to turn to food for emotional satisfaction or freedomr from emotional pain.
Thus, the first and most important step for successful weight loss is to begin to condition your mind to view food, first and foremost as a source of nutrition and sustenance rather than an emotional cue.