Don't diet! Change your lifestyle. Do things that you know you can incorporate into your lifestyle. Do small things consistently rather than one massive effort for a few weeks, which will be a lot less stressful for you in order to get used to the change.
Set realistic goals, visualize what you want to accomplish and by when & stick with it!
Understand that most of the battle is going to be fought between your ears.
Adequate rest and sleep is crucial!
You have to reduce your stress levels! Practice meditation or yoga to keep a clear mind for your work & personal life.
Eat more often! Eat more meals a day, but eat smaller healthier portions.
Don't do Fancy Diets (Fasting diets, crash diets, water diets, etc.) They just slow down your metabolism in order to help you burn fat & lose weight!