During the diet planning process, don't ignore the necessity for a maintenance plan for the period after you've met your weight loss goals. It's an unfortunate fact of dieting that most people regain all the weight they've lost and then some once they relax after dieting.
During diet planning, you're going to be faced with a decision of getting rid of all your good-tasting tempting food and replacing it with food that's good for you but not so tasty. That can be effective, but it can also sabotage you later. If you don't learn to exercise your willpower, you'll never be able to control your eating habits.